ZX Spectrum

The ZX Spectrum (Pronounced "Zed Ecks Spec-trum" in its original British English branding) is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research Ltd. Referred to during development as the ZX81 Colour and ZX82,[2][3] the machine was launched as the ZX Spectrum by Sinclair to highlight the machine's colour display, compared with the black-and-white of its predecessor, the Sinclair ZX81.[4] The Spectrum was released in eight different models, ranging from the entry level model with 16 KB RAM released in 1982 to the ZX Spectrum +3 with 128 KB RAM and built in floppy disk drive in 1987, together they sold in excess of 5 million units worldwide[5] Kingston HyperX-KHX1333C7D3K2/2G<o:p>

The Spectrum was among the first mainstream audience home computers in the UK, similar in significance to the Commodore 64 in the USA. The introduction of the ZX Spectrum led to a boom in companies producing software and hardware for the machine,[6] the effects of which are still seen;[1] some credit it as the machine which launched the UK IT industry.[7] Licensing deals and clones followed, and earned Clive Sinclair a knighthood for "services to British industry".[8] Kingston DDR3-KHX1333C7D3K2/4G<o:p>

The Commodore 64, BBC Microcomputer and later the Amstrad CPC range were major rivals to the Spectrum in the UK market during the early 1980s. The ZX Spectrum has enjoyed a resurgence in popularity thanks to the accessibility of ZX Spectrum emulators, allowing 1980s video game enthusiasts to enjoy classic titles without the long loading times associated with data cassettes. Over 20,000 titles have been released since the Spectrum's launch and new titles continue to be released, with over 60 new ones in 2009.<o:p>

ZX Spectrum 48K motherboard (Issue 3B — 1983, heat sink removed)<o:p>

The Spectrum is based on a Zilog Z80A CPU running at 3.5 MHz (or NEC D780C-1 clone). The original model Spectrum has 16 KB (16×1024 bytes) of ROM and either 16 KB or 48 KB of RAM. Hardware design was by Richard Altwasser of Sinclair Research, and the machine's outward appearance was designed by Sinclair's industrial designer Rick Dickinson.[6] Kingston DDR3 1600mhz 4GB<o:p>

Video output is through an RF modulator and was designed for use with contemporary portable television sets, for a simple colour graphic display. Text can be displayed using 32 columns × 24 rows of characters from the ZX Spectrum character set or from a set provided within an application, from a palette of 15 shades: seven colours at two levels of brightness each, plus black.[9] The image resolution is 256×192 with the same colour limitations.[10] To conserve memory, colour is stored separate from the pixel bitmap in a low resolution, 32×24 grid overlay, corresponding to the character cells. Altwasser received a patent for this design.[11] Kingston DDR3 1600mhz 2gb<o:p>

An "attribute" consists of a foreground and a background colour, a brightness level (normal or bright) and a flashing "flag" which, when set, causes the two colours to swap at regular intervals.[10] Unfortunately, this scheme leads to what was dubbed colour clash or attribute clash with some bizarre effects in the animated graphics of arcade style games. This problem became a distinctive feature of the Spectrum and an in-joke among Spectrum users, as well as a point of derision by advocates of other systems. Other machines available around the same time, for example the Amstrad CPC, did not suffer from this limitation. The Commodore 64 used colour attributes in a similar way, but a special multicolour mode, hardware sprites and hardware scrolling were used to avoid attribute clash. Kingston DDR3 1800mhz 4gb <o:p>

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Sound output is through a beeper on the machine itself. This is capable of producing one channel with 10 octaves. The machine also includes an expansion bus edge connector and audio in/out ports for the connection of a cassette recorder for loading and saving programs and data.<o:p>

Firmware<o:p>

The machine's Sinclair BASIC interpreter is stored in ROM (along with fundamental system-routines) and was written by Steve Vickers on contract from Nine Tiles Ltd. The Spectrum's chiclet keyboard (on top of a membrane, similar to calculator keys) is marked with BASIC keywords, so that, for example, pressing "G" when in programming mode would insert the BASIC command GO TO.[12] Kingston DDR3 1800mhz 2gb<o:p>

The BASIC was developed from that used on the ZX81 and a ZX81 BASIC program can be typed into a Spectrum largely unmodified, but Spectrum BASIC included many extra features making it easier to use. It also featured a full ASCII character set, missing from the ZX81 which did not feature lower-case letters. Spectrum BASIC included extra keywords for the more advanced display and sound, and also supported multi-statement lines. The cassette interface was also much more advanced, saving and loading around four times faster than the ZX81, and much more reliably. As well as being able to save programs, the Spectrum could in addition save the contents of arrays, the contents of the screen memory, and the contents of any defined range of memory addresses. Kingston DDR3 1333C7D3K2/4G<o:p>

Sinclair Research models<o:p>

Pre-production designs<o:p>

Rick Dickinson came up with a number of designs for the "ZX82" project before the final ZX Spectrum design. A number of the keyboard legends changed during the design phase including ARC becoming CIRCLE, FORE becoming INK and BACK becoming PAPER.[2]<o:p>

ZX Spectrum 16K/48K<o:p>

ZX Spectrum 16K/48K (Dimensions (mm): 233x144x30 (WxHxD) @ ~552 grams).[13] Kingston DDR3-KHX1333C7D3K2/4G<o:p>

The original ZX Spectrum is remembered for its rubber keyboard, diminutive size and distinctive rainbow motif. It was originally released in 1982 with 16 KB of RAM for £125 Sterling or with 48 KB for £175;[14] these prices were later reduced to £99 and £129 respectively.[15] Owners of the 16 KB model could purchase an internal 32 KB RAM upgrade, which for early "Issue 1" machines consisted of a daughterboard. Later issue machines required the fitting of 8 dynamic RAM chips and a few TTL chips. Users could mail their 16K Spectrums to Sinclair to be upgraded to 48 KB versions. To reduce the price, the 32 KB extension used eight faulty 64 kilobit chips with only one half of their capacity working and/or available.[16] External 32 KB RAM packs that mounted in the rear expansion slot were also available from third parties. Both machines had 16 KB of onboard ROM. KINGSTON DDR3 KHX1600C7D3K2/4GX<o:p>

About 60,000 "Issue 1" ZX Spectrums were manufactured; they can be distinguished from later models by the colour of the keys (light grey for Issue 1, blue-grey for later models).[17]<o:p>

ZX Spectrum+<o:p>

ZX Spectrum+ (Dimensions (mm): 319x149x38 (WxHxD))[13]<o:p>

Planning of the ZX Spectrum+ started in June 1984,[18] and the machine was released in October the same year.[19] This 48 KB Spectrum (development code-name TB[18]) introduced a new QL-style case with an injection-moulded keyboard and a reset button. Electronically, it was identical to the previous 48 KB model. It retailed for £179.95.[20] A DIY conversion-kit for older machines was also available. Early on, the machine outsold the rubber-key model 2:1;[18] however, some retailers reported a failure rate of up to 30%, compared with a more usual 5-6%.[19] KINGSTON DDR3 KHX1600C7D3K2/4G<o:p>

ZX Spectrum 128<o:p>

ZX Spectrum 128<o:p>

Sinclair developed the ZX Spectrum 128 (code-named Derby) in conjunction with their Spanish distributor Investrónica.[21] Investrónica had helped adapt the ZX Spectrum+ to the Spanish market after the Spanish government introduced a special tax on all computers with 64 KB RAM or less which did not support the Spanish alphabet (such as ñ) and show messages in Spanish.[22]<o:p>

New features included 128 KB RAM, three-channel audio via the AY-3-8912 chip, MIDI compatibility, an RS-232 serial port, an RGB monitor port, 32 KB of ROM including an improved BASIC editor, and an external keypad. KINGSTON DDR3 KHX1333C9D3K2/4G<o:p>

The machine was simultaneously presented for the first time and launched in September 1985 at the SIMO '85 trade show in Spain, with a price of 44,250 pesetas. Because of the large number of unsold Spectrum+ models, Sinclair decided not to start selling in the UK until January 1986 at a price of £179.95.[23] No external keypad was available for the UK release, although the ROM routines to use it and the port itself, which was hastily renamed "AUX", remained. KINGSTON DDR3 KHX1333C9D3K2/2G<o:p>

The Z80 processor used in the Spectrum has a 16-bit address bus, which means only 64 KB of memory can be directly addressed. To facilitate the extra 80 KB of RAM the designers used bank switching so that the new memory would be available as eight pages of 16 KB at the top of the address space. The same technique was also used to page between the new 16 KB editor ROM and the original 16 KB BASIC ROM at the bottom of the address space. KINGSTON DDR3 KHX1333C7D3k3/6GX<o:p>

The new sound chip and MIDI out abilities were exposed to the BASIC programming language with the command PLAY and a new command SPECTRUM was added to switch the machine into 48K mode, keeping the current BASIC program intact (although there is no way to switch back to 128K mode). To enable BASIC programmers to access the additional memory, a RAM disk was created where files could be stored in the additional 80 KB of RAM. The new commands took the place of two existing user-defined-character spaces causing compatibility problems with some BASIC programs. KINGSTON DDR3 KHX1333C7D3k3/3GX<o:p>

The Spanish version had the "128K" logo in white while the English one had the same logo in red.<o:p>

Amstrad models<o:p>

ZX Spectrum +2<o:p>

ZX Spectrum +2<o:p>

The ZX Spectrum +2 was Amstrad's first Spectrum, coming shortly after their purchase of the Spectrum range and "Sinclair" brand in 1986. The machine featured an all-new grey case featuring a spring-loaded keyboard, dual joystick ports, and a built-in cassette recorder dubbed the "Datacorder" (like the Amstrad CPC 464), but was in most respects identical to the ZX Spectrum 128. The main menu screen lacked the Spectrum 128's "Tape Test" option, and the ROM was altered to account for a new 1986 Amstrad copyright message. These changes resulted in minor incompatibility problems with software that accessed ROM routines at certain addresses. Production costs had been reduced and the retail price dropped to £139–£149.[24] KINGSTON DDR3 KHX1600C7D3K3/6GX<o:p>

The new keyboard did not include the BASIC keyword markings that were found on earlier Spectrums, except for the keywords LOAD, CODE and RUN which were useful for loading software. This was not a major issue however, as the +2 boasted a menu system, almost identical to the ZX Spectrum 128, where one could switch between 48k BASIC programming with the keywords, and 128k BASIC programming in which all words (keywords and otherwise) must be typed out in full (although the keywords are still stored internally as one character each). Despite these changes, the layout remained identical to that of the 128. KINGSTON DDR3 KHX1600C9D3K3/3GX<o:p>

ZX Spectrum +2A<o:p>

ZX Spectrum +2A<o:p>

The ZX Spectrum +2A was produced to homogenise Amstrad's range in 1987. Although the case reads "ZX Spectrum +2", the +2A/B is easily distinguishable from the original +2 as the case was restored to the standard Spectrum black.<o:p>

The +2A was derived from Amstrad's +3 4.1 ROM model, using a new motherboard which vastly reduced the chip count, integrating many of them into a new ASIC. The +2A replaced the +3's disk drive and associated hardware with a tape drive, as in the original +2. Originally, Amstrad planned to introduce an additional disk interface, but this never appeared. If an external disk drive was added, the "+2A" on the system OS menu would change to a +3. As with the ZX Spectrum +3, some older 48K, and a few older 128K, games were incompatible with the machine. kingston laptop DDR2(667)  1GB<o:p>

ZX Spectrum +2B<o:p>

The ZX Spectrum +2B signified a manufacturing move from Hong Kong to Taiwan later in 1987.[25]<o:p>

ZX Spectrum +3<o:p>

ZX Spectrum +3<o:p>

The ZX Spectrum +3 looked similar to the +2 but featured a built-in 3-inch floppy disk drive (like the Amstrad CPC 6128) instead of the tape drive, and was in a black case. It was launched in 1987, initially retailed for £249[26] and then later £199[27] and was the only Spectrum capable of running the CP/M operating system without additional hardware. kingston laptop  DDR2(667)  2GB<o:p>

The +3 saw the addition of two more 16 KB ROMs. One was home to the second part of the reorganised 128 ROM and the other hosted the +3's disk operating system. This was a modified version of Amstrad's AMSDOS, called +3DOS. These two new 16 KB ROMs and the original two 16 KB ROMs were now physically implemented together as two 32 KB chips. To be able to run CP/M, which requires RAM at the bottom of the address space, the bank-switching was further improved, allowing the ROM to be paged out for another 16 KB of RAM. kingston laptop DDR2(800)  1GB<o:p>

Such core changes brought incompatibilities:<o:p>

Removal of several lines on the expansion bus edge connector (video, power, and IORQGE); caused many external devices problems; some such as the VTX5000 modem could be used via the "FixIt" device<o:p>

Dividing ROMCS into 2 lines, to disable both ROMskingston laptop -DDR2(800)-2GB<o:p>

Reading a non-existent I/O port no longer returned the last attribute; caused some games such as Arkanoid to be unplayable<o:p>

Memory timing changes; some of the RAM banks were now contended causing high-speed colour-changing effects to fail<o:p>

The keypad scanning routines from the ROM were removed<o:p>

move 1 byte address in ROM<o:p>

Some older 48K, and a few older 128K, games were incompatible with the machine.<o:p>

The +3 was the final official model of the Spectrum to be manufactured, remaining in production until December 1990. Although still accounting for one third of all home computer sales in the UK at the time[clarification needed][citation needed], production of the model was ceased by Amstrad at that point. kingsto laptop DDR3(1066)  1GB<o:p>

Clones<o:p>

Didaktik M<o:p>

See also: list of ZX Spectrum clones<o:p>

Sinclair licensed the Spectrum design to Timex Corporation in the United States. An enhanced version of the Spectrum with better sound, graphics and other modifications was marketed in the USA by Timex as the Timex Sinclair 2068. Timex's derivatives were largely incompatible with Sinclair systems. However, some of the Timex innovations were later adopted by Sinclair Research. A case in point was the abortive Pandora portable Spectrum, whose ULA had the high resolution video mode pioneered in the TS2068. Pandora had a flat-screen monitor and Microdrives and was intended to be Sinclair's business portable. When Alan Sugar bought the computer side of Sinclair it got ditched (a conversation with UK computer journalist Guy Kewney went thus: AS: "Have you seen it?" GK: "Yes" AS: "Well then.").[28] kingston-Laptop-DDR3(1066)-2GB<o:p>

In the UK, Spectrum peripheral vendor Miles Gordon Technology (MGT) released the SAM Coupé as a potential successor with some Spectrum compatibility. However, by this point, the Commodore Amiga and Atari ST had taken hold of the market, leaving MGT in eventual receivership.<o:p>

Many unofficial Spectrum clones were produced, especially in the former Eastern Bloc countries (e.g. in Romania, several models were produced (Tim-S, HC85, HC91, Cobra, Junior, CIP, CIP 3, Jet) , some featuring CP/M and a 5.25"/3.5" floppy disk) and South America (e.g. Microdigital TK 90X and TK 95). In the Soviet Union, ZX Spectrum clones were assembled by thousands of small start-ups and distributed though poster ads and street stalls. Over 50 such clone models existed.[29] Some of them are still being produced, such as the Pentagon and ATM Turbo. In India, Decibells Electronics introduced a licensed version of the Spectrum+ in 1986. Dubbed the "db Spectrum+", it did reasonably well in the Indian market and sold quite a few thousand until 1990 when the market died away. kingston-Laptop-DDR3(1333)-1GB)<o:p>

Peripherals<o:p>

Several peripherals for the Spectrum were marketed by Sinclair: the ZX Printer was already on the market,[30] as the ZX Spectrum expansion bus was backwards-compatible with that of the ZX81.<o:p>

The ZX Interface 1 add-on module included 8 KB of ROM, an RS-232 serial port, a proprietary LAN interface (called ZX Net), and an interface for the connection of up to eight ZX Microdrives – somewhat unreliable but speedy tape-loop cartridge storage devices released in July 1983.[31][32] These were later used in a revised version on the Sinclair QL, whose storage format was electrically compatible but logically incompatible with the Spectrum's. Sinclair also released the ZX Interface 2 which added two joystick ports and a ROM cartridge port.[33] kingston Laptop DDR3(1333) 2GB<o:p>

There were also a plethora of third-party hardware addons. The better known of these included the Kempston joystick interface, the Morex Peripherals Centronics/RS-232 interface, the Currah Microspeech unit (speech synthesis),[34] Videoface Digitiser,[35] RAM pack, the Cheetah Marketing SpecDrum,[36] a drum machine, and the Multiface,[37] a snapshot and disassembly tool from Romantic Robot. Keyboards were especially popular in view of the original's notorious "dead flesh" feel.[38] kingston DDR2(667) 1GB<o:p>

There were numerous disk drive interfaces, including the Abbeydale Designers/Watford Electronics SPDOS, Abbeydale Designers/Kempston KDOS and Opus Discovery. The SPDOS and KDOS interfaces were the first to come bundled with Office productivity software (Tasword Word Processor, Masterfile database and OmniCalc spreadsheet). This bundle, together with OCP's Stock Control, Finance and Payroll systems, introduced many small businesses to a streamlined, computerised operation. The most popular floppy disk systems (except in East Europe) were the DISCiPLE and +D systems released by Miles Gordon Technology in 1987 and 1988 respectively. Both systems had the ability to store memory images onto disk snapshots could later be used to restore the Spectrum to its exact previous state. They were also both compatible with the Microdrive command syntax, which made porting existing software much simpler.[39] kingston- DDR2(667)-2GB<o:p>

During the mid-1980s, Telemap Group Ltd launched a fee-based service allowing users to connect their ZX Spectrums via a Prism Micro Products VTX5000 modem to a vieWData service known as Micronet 800, hosted by Prestel. This service pre-dated the web, but offered many of the services now considered commonplace.<o:p>

Software<o:p>

A screenshot from Rebelstar, a well-known Spectrum game<o:p>

Main article: ZX Spectrum software<o:p>

The Spectrum enjoys a vibrant, dedicated fan-base.[40][41] Since it was cheap and simple to learn to use and program, the Spectrum was the starting point for many programmers.[1] The hardware limitations of the Spectrum imposed a special level of creativity on game designers, and so many Spectrum games are very creative and playable even by today's standards.[42] The early Spectrum models' great success as a games platform came in spite of its lack of built-in joystick ports, primitive sound generation, and colour support that was optimised for text display.[43] WD passport essential 500gb<o:p>

The Spectrum family enjoys a very large software library of more than 20,000 titles[44] which is still increasing. While most of these are games, the library is very diverse, including programming language implementations, databases (e.g. VU-File[45]), word processors (e.g. Tasword II[46]), spreadsheets (e.g. VU-Calc[45]), drawing and painting tools (e.g. OCP Art Studio[47]), and even 3D-modelling (e.g. VU-3D[48][49]) and archaeology software[50] amongst many other types.[51]<o:p>

DistributionWD passport essential 320GB blue<o:p>

Most Spectrum software was originally distributed on audio cassette tapes. The Spectrum was intended to work with a normal domestic cassette recorder,[52] and despite differences in audio reproduction fidelity, the software loading process was quite reliable, if somewhat slow (by today's standards).<o:p>

Although the ZX Microdrive was initially greeted with good reviews,[53] it never took off as a distribution method due to worries about the quality of the cartridges and piracy.[54] Hence the main use became to complement tape releases, usually utilities and niche products like the Tasword word processing software and Trans Express, (a tape to microdrive copying utility). No games are known to be exclusively released on Microdrive. WD passport essential 320GB silver<o:p>

Despite the popularity of the DISCiPLE and +D systems, most software released for them took the form of utility software. The ZX Spectrum +3 enjoyed much more success when it came to commercial software releases on floppy disk. More than 700 titles were released on 3-inch disk from 1987 to 1997.[44]<o:p>

Software was also distributed through print media; magazines[55] and books.[56] The reader would type the Sinclair BASIC program listing into the computer by hand, run it, and could save it to tape for later use. The software distributed in this way was in general simpler and slower than its assembly language counterparts. Magazines also printed long lists of checksummed hexadecimal digits with machine code games or tools. WD passport essential 500GB red<o:p>

Another software distribution method was to broadcast the audio stream from the cassette on another medium and have users record it onto an audio cassette themselves. In radio or television shows in many European countries, the host would describe a program, instruct the audience to connect a cassette tape recorder to the radio or TV and then broadcast the program over the airwaves in audio format.[57] Some magazines distributed 7" 33 rpm flexidisc records, a variant of regular vinyl records which could be played on a standard record player.[58] These disks were known as floppy ROMs.<o:p>

Copying and backup softwareWD passport essential 320GB white<o:p>

A screenshot from Elite game<o:p>

Many copiers—utilities to copy programs from audio tape to another tape, microdrive tapes, and later on diskettes—were available for the Spectrum.[59] As a response to this, publishers introduced copy protection measures to their software, including different loading schemes.[60] Other methods for copy prevention were also used including asking for a particular word from the documentation included with the game—often a novella like in Silicon Dreams trilogy—or another physical device distributed with the software—e.g. Lenslok as used in Elite. Special hardware, such as Romantic Robot's Multiface, was able to dump a copy of the ZX Spectrum RAM to disk/tape at the press of a button, entirely circumventing the copy protection systems. WD passport essential 500GB white<o:p>

Most Spectrum software has, in recent years, been converted to current media and is available for download. One popular program for converting Spectrum files from tape is Taper; it allows connecting a cassette tape player to the line in port of a sound card, or—through a simple home-built device—to the parallel port of a PC.[61] Once in files on a host machine, the software can be executed on one of many emulators, on virtually any platform available today.<o:p>

The largest on-line archive of ZX Spectrum software is World of Spectrum, with more than 21,000 titles. The legality of this practice is still in question and while a number of copyright holders have explicitly objected to the posting of their software, others have given their permission for their games to be archived as part of the preservation project.[62] WD passport essential 500GB red<o:p>

Notable developers<o:p>

A number of current leading games developers and development companies began their careers on the ZX Spectrum, including David Perry of Shiny Entertainment, and Tim and Chris Stamper (founders of Ultimate Play The Game, now known as Rare, maker of many famous titles for Nintendo and Microsoft game consoles). Other prominent games developers include Julian Gollop (Chaos, Rebelstar, X-COM series), Matthew Smith (Manic Miner, Jet Set Willy), Jon Ritman (Match Day, Head Over Heels), The Oliver Twins (the Dizzy series), Clive Townsend (Saboteur), Pete Cooke (Tau Ceti), Mike Singleton (The Lords of Midnight,War In Middle Earth), and Alan Cox.[63] Although the Spectrum's audio hardware was not as capable as that of the Commodore 64, computer musicians David Whittaker and Tim Follin produced notable multi-channel music for the machine. WD passport essential 500GB black<o:p>

Jeff Minter ported some of his Commodore VIC-20 games for the ZX Spectrum.[64]<o:p>

Community<o:p>

The ZX Spectrum enjoyed a very strong community early on. Several dedicated magazines were released including Sinclair User (1982), Your Sinclair (1983) and CRASH (1984). Early on they were very technically oriented with type-in programs and machine code tutorials. Later on they became almost completely game-oriented. Several general contemporary computer magazines covered the ZX Spectrum in more or less detail. They included Computer Gamer, Computer and Video Games, Computing Today, Popular Computing Weekly, Your Computer and The Games Machine.[65] WD Passport Essential SE 1TB USB 3.0<o:p>

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Digital single-lens reflex camera

<o:p> 

Olympus E-420 Four Thirds digital SLR.<o:p>

Most digital single-lens reflex cameras (digital SLR or DSLR) are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera.<o:p>

The basic operation of a DSLR is as follows: for viewing purposes, the mirror reflects the light coming through the attached lens upwards at a 90 degree angle. It is then reflected three times by the roof pentaprism, rectifying it for the photographer's eye. (Note that the diagram below incorrectly shows a non-roof pentaprism.) During exposure, the mirror assembly swings upward, the aperture narrows (if stopped down, or set smaller than wide open), and a shutter opens, allowing the lens to project light onto the image sensor. Sony VAIO VGN-FZ11E Battery<o:p>

 A second shutter then covers the sensor, ending the exposure, and the mirror lowers while the shutter resets. The period that the mirror is flipped up is referred to as "viewfinder blackout". A fast-acting mirror and shutter is preferred so as to not delay an action photo.<o:p>

All of this happens automatically over a period of milliseconds, with cameras designed to do this 3–10 times per second. Sony VAIO VGN-FZ11L Battery<o:p>

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DSLRs are often preferred by professional still photographers because they allow an accurate preview of framing close to the moment of exposure, and because DSLRs allow the user to choose from a variety of interchangeable lenses. Most DSLRs also have a function that allows accurate preview of depth of field.<o:p>

Many professionals also prefer DSLRs for their larger sensors compared to most compact digitals. DSLRs have sensors which are generally closer in size to the traditional film formats that many current professionals started out using. These large sensors allow for similar depths of field and picture angle to film formats, as well as their comparatively high signal to noise ratio. Sony VAIO VGN-FZ11M Battery<o:p>

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The term DSLR generally refers to cameras that resemble 35 mm format cameras, although some medium format cameras are technically DSLRs.<o:p>

 [edit]Comparison with digital point-and-shoot camera<o:p>

<o:p> 

The reflex design scheme is a major difference between a DSLR and an ordinary digital point-and-shoot camera, which typically exposes the sensor constantly to the light projected by the lens, allowing the camera's screen to be used as an electronic viewfinder. Sony VAIO VGN-FZ11S Battery<o:p>

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A camera based on the single-lens reflex (SLR) principle uses a mirror to show in a viewfinder the image that will be captured. The cross-section (side-view) of the optical components of an SLR shows how the light passes through the lens assembly (1), is reflected into the pentaprism by the reflex mirror (which must be at an exact 45 degree angle) (2) and is projected on the matte focusing screen (5). Via a condensing lens (6) and internal reflections in the roof pentaprism (7) the image is projected through the eyepiece (8) to the photographer's eye. Focusing is either automatic, activated by pressing half-way on the shutter release or a dedicated AF button, as is mainly the case with an autofocusing film SLR; or manual, where the photographer manually focuses the lens by turning a lens ring on the lens barrel. When an image is photographed, the mirror swings upwards in the direction of the arrow, the focal-plane shutter (3) opens, and the image is projected and captured on the sensor (4), after which actions, the shutter closes, the mirror returns to the 45 degree angle, the diaphragm reopens, and the built in drive mechanism re-tensions the shutter for the next exposure. Sony VAIO VGN-FZ11Z Battery<o:p>

There is often a ring of soft material around the focusing screen, which helps to both cushion the impact of the mirror slapping up and helps seal the mirror box from light entering through the eye piece.[1] Some high end cameras incorporate a shutter into the eyepiece to further eliminate light that may enter there during long exposures.<o:p>

[edit]Phase-detection autofocus<o:p>

The diagram shown here is an over-simplification in that it omits the sensors used to activate the drive for the autofocus system. Those sensors reside at the bottom of the mirror box. In such a system, the main mirror is slightly translucent in the center, which allows light to pass through it to a secondary mirror which reflects light to the sensors below. Sony VAIO VGN-FZ130E/B Battery<o:p>

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DSLRs typically use a phase detection autofocus system. This method of focus is very fast, and results in less focus "searching", but requires the incorporation of a special sensor into the optical path, so it is usually only used in SLR designs. Digicams that use the main sensor to create a live preview on the LCD or electronic viewfinder must use contrast-detect autofocus instead, which is slower in some implementations. Sony VAIO VGN-FZ140E Battery<o:p>

<o:p> 

[edit]DSLR optical viewfinder vs. digital point-and-shoot camera LCD<o:p>

Depending on the viewing position of the reflex mirror (down or up), the light from the scene can only reach either the viewfinder or the sensor. Therefore, many older DSLRs do not provide "live preview" (allowing focusing, framing, and depth-of-field preview using the display), a facility that is always available on digicams although today most DSLRs offer live view. Sony VAIO VGN-FZ140E/B Battery<o:p>

<o:p> 

The advantages of an optical viewfinder are that it alleviates eye-strain sometimes caused by electronic view finders (EVF), and that it constantly shows (except during the time for the sensor to be exposed) the exact image that will be exposed because its light is routed directly from the lens itself. Compared to ordinary digital cameras with their LCDs and/or electronic viewfinders the advantage is that there is no time lag in the image; it is always correct as it is being "updated" at the speed of light. This is important for action and/or sports photography, or any other situation where the subject or the camera is moving too quickly. Furthermore, the "resolution" of the viewed image is much better than that provided by an LCD or an electronic viewfinder, which can be important if manual focusing is desired for precise focusing, as would be the case in macro photography and "micro-photography" (with a microscope). Sony VAIO VGN-FZ140N/B Battery<o:p>

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Compared to some low cost cameras that provide an optical viewfinder that uses a small auxiliary lens, the DSLR design has the advantage of being parallax-free; that is, it never provides an off-axis view.<o:p>

A disadvantage of the DSLR optical viewfinder system is that while it is used it prevents the possibility of using the LCD for viewing and composing the picture before taking it. Some people prefer to compose pictures on the display – for them this has become the de-facto way to use a camera. Electronic viewfinders may also provide a brighter display in low light situations, as the picture can be electronically amplified; conversely, LCDs can be difficult to see in very bright sunlight. Sony VAIO VGN-FZ15 Battery<o:p>

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[edit]DSLRs with live preview<o:p>

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<o:p> 

Nikon D90 in Liveview mode<o:p>

Early DSLRs lacked the ability to show the optical viewfinder's image on the LCD display, a feature known as live preview. Live preview is useful in situations where the camera's eye-level viewfinder cannot be used, such as Underwater photography where the camera is enclosed in a plastic waterproof case.<o:p>

Olympus introduced the Olympus E-10 in the summer of 2000, which was the first DSLR with live preview – albeit an atypical design with a fixed lens. In late 2008, some DSLRs from Canon, Nikon, Olympus, Panasonic, Leica, Pentax, Samsung and Sony all provide continuous live preview as an option. Additionally, the Fujifilm FinePix S5 Pro[2] offers 30 seconds of live preview. Sony VAIO VGN-FZ15G Battery<o:p>

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On most DSLRs that offer live preview, the phase detection autofocus system does not work in the live preview mode, and the DSLR switches to a slower contrast system commonly found in point & shoot cameras.<o:p>

Some live preview systems make use of the primary sensor to provide the image on the LCD (which is the way all non-DSLR digicams work), and some systems use a secondary sensor. Possible advantages of using a secondary sensor for live preview is to avoid additional noise that might result from the primary sensor heating up from continuous use and allowing faster auto-focus.[3] Sony VAIO VGN-FZ15T Battery<o:p>

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A new feature via a separate software package introduced from Breeze Systems in October, 2007, features live view from a distance. The software package is named "DSLR Remote Pro v1.5" and enables support for the Canon EOS 40D and 1D Mark III.[4]<o:p>

[edit]High definition DSLRs (HDSLRs)<o:p>

Introduced in 2008, HDSLRs are DSLRs which, in addition to taking still photographs, offer a movie mode capable of recording high definition motion video. This feature parallels the evolution of compact digital cameras, many of which also offer HD movie mode. The first DSLR to shoot HD was the Nikon D90, which captures video at 720p24 (1280x720 resolution at 24 fps) using an APS-sized sensor. The second, Canon EOS 5D Mark II, captured video at 1080p30 (1920x1080 resolution at 30 fps), and in 2010 a firmware update was released that allows 1080p24 (1920x1080 resolution at 24 fps) using a full frame 35mm CMOS sensor. Sony VAIO VGN-FZ160E Battery<o:p>

 The 720/24p of the Nikon D90 is not a compliant frame rate for high-definition television broadcast, Blu-ray disc mastering[5] or Digital Cinema Initiatives (DCI). The first HDSLR to shoot a standard HD broadcast, Blu-ray and digital cinema format is the Panasonic Lumix GH1 (both 1920x1080/23.976p and 1280x720/59.94p). With the release of the professional Canon 1D Mark IV, the entry level professional Canon 7D and the consumer model Canon 550D (Rebel T2i), there are now four HDSLRs that can shoot in these standard/broadcast compliant resolutions and frame rates, with the Canon EOS 5D Mark II adding 24p and industry compliance with the release of firmware version 2.0.3/2.0.4.[2] Sony VAIO VGN-FZ160E/B Battery<o:p>

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Less than a year after the introduction of the first HDSLR, "HD movie mode" was incorporated into entry-level DSLR camera models, the first being the Canon EOS 500D (Rebel T1i) and Nikon D5000. The 500D supports both 720p30 and a limited 1080p mode which captures 20 fps. The D5000's movie mode is comparable to the D90, with a maximum capture mode of 720p24. These entry-level cameras also use non-standard resolution and frame rate combinations.<o:p>

On 20 May 2009, Pentax announced its K-7 HDSLR. It supports non-broadcast/blu-ray/DCI compliant HD capture at 30 fps, in both 720p resolution, and an unusual non-standard resolution mode of 1536×1024 which matches the 3:2 aspect ratio of the image sensor.<o:p>

Sony VAIO VGN-FZ17 Battery<o:p>

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[edit]DSLR lenses<o:p>

<o:p> 

<o:p> 

<o:p> 

Nikon AF Nikkor 50mm full frame Prime lens<o:p>

<o:p> 

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Nikon AF Nikkor 18-70mm (APS-C) Zoom lens<o:p>

Main articles: Photographic lens and Lenses for SLR and DSLR cameras<o:p>

The ability to exchange lenses, to select the best lens for the current photographic need, and to allow the attachment of specialized lenses, is a key to the popularity of DSLR cameras.<o:p>

[edit]Lens mounts and lens manufacturers<o:p>

Further information: crop factorSony VAIO VGN-FZ17G Battery<o:p>

<o:p> 

Interchangeable lenses for SLRs and DSLRs are built to operate correctly with a specific lens mount that is generally unique to each brand. A photographer will often use lenses made by the same manufacturer as the camera body (for example, Canon EF lenses on a Canon body) although there are also many independent lens manufacturers, such as Sigma, Tamron, Tokina, and Vivitar, to name a few, that make lenses for a variety of different lens mounts. There are also lens adapters that allow a lens for one lens mount to be used on a camera body with a different lens mount but with often reduced functionality. Sony VAIO VGN-FZ18 Battery<o:p>

<o:p> 

Many lenses are mountable, "diaphragm-and-meter-compatible", on modern DSLRs and on older film SLRs that use the same lens mount. Most DSLR manufacturers have introduced lines of lenses with image circles and focal lengths optimized for the smaller sensors generally offered for existing 35 mm mount DSLRs, mostly in the wide angle range. These lenses tend not to be completely compatible with full frame sensors or 35 mm film because of the smaller imaging circle[6] and, with some Canon EF-S lenses, interference with the reflex mirrors on full-frame bodies. Several manufacturers produce full-frame digital SLR cameras that allow lenses designed for the 35 mm film frame to operate at their intended angle of view. Sony VAIO VGN-FZ180E Battery<o:p>

<o:p> 

[edit]DSLR design considerations<o:p>

<o:p> 

[edit]Pentaprism vs. penta-mirror<o:p>

Most of the entry level DSLRs use a pentamirror instead of the traditional pentaprism. The pentamirror design is composed mostly of plastic and is lighter and cheaper to produce — however, the image in the viewfinder is usually darker.<o:p>

<o:p> 

<o:p> 

Drawing showing the relative sizes of sensors used in current digital cameras.<o:p>

[edit]Sensor size and image quality<o:p>

Main article: Image sensor format<o:p>

Image sensors used in DSLRs come in a range of sizes. The very largest are the ones used in "medium format" cameras, typically via a "digital back" which can be used as an alternative to a film back. Because of the manufacturing costs of these large sensors the price of these cameras is typically over $20,000 as of December 2007. Sony VAIO VGN-FZ18T Battery<o:p>

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With the exception of medium format DSLRs, the largest sensors are referred to as "full-frame" and are the same size as 35 mm film (135 film, image format 24×36 mm); these sensors are used in high-end DSLRs such as the Canon EOS-1Ds Mark III, the Canon EOS 5D Mark II, the Nikon D700, the Nikon D3, the Nikon D3X, the Sony Alpha 850 and the Sony Alpha 900. Most modern DSLRs use a smaller sensor commonly referred to as APS-C sized, that is, approximately 22 mm × 15 mm, a little smaller than the size of an APS-C film frame, or about 40% of the area of a full-frame sensor. Other sensor sizes found in DSLRs include the Four Thirds System sensor at 26% of full frame, APS-H sensors (used, for example, in the Canon EOS-1D Mark III) at around 61% of full frame, and the Foveon X3 sensor at 33% of full frame. Sony VAIO VGN-FZ18M Battery<o:p>

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The sensors used in current DSLRs are much larger than the sensors found in digicam-style cameras, most of which use sensors known as 1/2.5", whose area is only 3% of a full frame sensor. Even high-end digicams such as the Canon PowerShot G9/G10/G11 or the Nikon CoolPix P5000/P6000 use sensors that are approximately 5% and 4% of the area of a full frame sensor, respectively. The current exceptions are the Micro Four Thirds system by Olympus and Panasonic, the Sigma DP1, which uses a Foveon X3 sensor, and the Leica X1. Leica offers an "S-System" DSLR with a 30×45mm array containing 37 million pixels.[7] This sensor is 56% larger than a full-frame sensor. Sony VAIO VGN-FZ18G Battery<o:p>

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There is a connection between sensor size and image quality; in general, a larger sensor provides lower noise, higher sensitivity, and increased latitude and dynamic range. There is also a connection between sensor size and depth of field, with the larger sensor resulting in shallower depth of field at a given aperture.<o:p>

 [edit]Depth-of-field control<o:p>

The lenses typically used on DSLRs have a wider range of apertures available to them, ranging from as large as f/1.0 to about f/32. Lenses for digicams rarely have true available aperture sizes much larger than f/2.8 or much smaller than f/5.6. Sony VAIO VGN-FZ18G Battery<o:p>

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The f/5.6 limitation is because lens designs of typical small sensor digicams already produce diffraction blur bigger than a few pixels at f/5.6.[10] Because of digicams' smaller sensors there are a limited number of apertures available that will produce an acceptably sharp image. Many digicams only have a two-stop range of apertures because at settings outside of these the image will become too soft because of limits of lens design at large apertures, or diffraction at smaller apertures. Sony VAIO VGN-FZ20 Battery<o:p>

 [11]<o:p>

The apertures that digicams have available give much more depth of field than equivalent angles of view on a DSLR. For example a 6 mm lens on a 2/3" sensor digicam has a field of view similar to a 24 mm lens on a 35 mm camera. At an aperture of f/2.8 the digicam (assuming a crop factor of 4) has a similar depth of field to that 35 mm camera set to f/11 – that's a four-stop difference. Put another way, with both cameras at f/2.8 and focused on a subject 1 meter from the camera, and both cameras zoomed to produce the same angle of view (35 mm camera will need to use larger focal length to produce same angle of view from same distance), the digicam might have a depth of field of 2 meters and the larger camera would have a depth of field of 0.3 meters.[12][13] Sony VAIO VGN-FZ21E Battery<o:p>

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[edit]Angle of view<o:p>

<o:p> 

<o:p> 

An APS-C format SLR (left) and a full-frame DSLR (right) show the difference in the size of the image sensors.<o:p>

The angle of view of a lens depends upon its focal length and the camera's image sensor size; a sensor smaller than 35 mm film format (36 mm × 24 mm frame) gives a narrower angle of view for a lens of a given focal length than a camera equipped with a full-frame (35 mm) sensor. As of 2008, only a few current DSLRs have full-frame sensors, including the Sony α 900, Canon EOS-1Ds Mark III, Canon 5D, Nikon D3x and Nikon D700. The scarcity of full-frame DSLRs is partly a result of the cost of such large sensors. Medium format size sensors, such as those used in the Mamiya ZD among others, are even larger than full-frame (35 mm) sensors, and capable of even greater resolution, and are correspondingly more expensive. Sony VAIO VGN-FZ21J Battery<o:p>

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The impact of sensor size on field of view is referred to as the "crop factor" or "focal length multiplier", which is a factor by which a lens focal length can be multiplied to give the full-frame-equivalent focal length for a lens. Typical APS-C sensors have crop factors of 1.5 to 1.7, so a lens with a focal length of 50 mm will give a field of view equal to that of a 75 mm to 85 mm lens on a 35 mm camera. The smaller sensors of Four Thirds System cameras have a crop factor of 2.0. Sony VAIO VGN-FZ21M Battery<o:p>

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While the crop factor of APS-C cameras effectively narrows the angle of view of long-focus (telephoto) lenses, making it easier to take close-up images of distant objects, wide-angle lenses suffer a reduction in their angle of view by the same factor.<o:p>

DSLRs with "crop" sensor size have slightly more depth-of-field than cameras with 35 mm sized sensors for a given angle of view. The amount of added depth of field for a given focal length can be roughly calculated by multiplying the depth of field by the crop factor. Shallower depth of field is often preferred by professionals for portrait work and to isolate a subject from its background.<o:p>

[edit]Mode dial<o:p>

Digital SLR cameras, along with most other digital cameras, generally have a mode dial to access standard camera settings or automatic scene-mode settings. Sometimes called a "PASM" dial, they typically provide as minimum Program, Aperture-priority, Shutter-priority, and full Manual modes. Scene modes vary and are inherently less customizable. They often include full-auto, landscape, portrait, action, macro, and night modes, among others. Professional DSLRs seldom contain automatic scene modes because professionals understand their equipment and can quickly adjust the settings to take the image that they want. Sony VAIO VGN-FZ21Z Battery<o:p>

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[edit]Dust reduction systems<o:p>

Main article: Dust reduction system<o:p>

The fact that it is possible to change lenses on a DSLR results in the possibility of dust entering the camera body and adhering to the image sensor. This can reduce image quality, and make it necessary to clean the sensor. Various techniques exist including using a cotton swab with various fluids or blowing with compressed air. Some people prefer to clean the sensor themselves and some send the camera in for service.[14]<o:p>

A method to prevent dust entering the chamber, by using a "dust cover" filter right behind the lens mount, was pioneered by Sigma in their first DSLR, the Sigma SD9, in 2002. Sony VAIO VGN-FZ25 Battery<o:p>

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Olympus pioneered a built-in sensor cleaning facility in their first DSLR that had a sensor exposed to air, the Olympus E-1, in 2003. Other DSLR manufacturers followed suit, and dust reduction systems are becoming common in DSLRs. There is some controversy as to how effective these systems are; see dust reduction system for more information.<o:p>

[edit]Medium format digital<o:p>

Many medium format roll-film SLRs can accept a digital camera back to turn the camera into a DSLR with very high image resolution and quality (typically 21–60 megapixels as of July 2009). However, the combination is very expensive and bulky, and more suited to still life than to action photography. Another potential disadvantage of medium format digital backs is that there are none currently available (as of early 2008) that incorporate a low-pass filter (aka optical anti-aliasing filter) except for the Mamiya ZD, which has a removable one. This is done to allow the maximum resolution to be extracted from a given image, but at the cost of moiré.[15][16]<o:p>

As of 2007 integrated medium formats like the Phase One 645 system[17], Hasselblad H System[18] and Leaf AFi[19] have started to appear. Sony VAIO VGN-FZ27 Battery<o:p>

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[edit]Unusual features<o:p>

On July 13, 2007, FujiFilm announced the FinePix IS Pro, which uses Nikon F-mount lenses. This camera, in addition to having live preview, has the ability to record in the infrared and ultraviolet spectra of light.[20]<o:p>

In August 2010 Sony released series of DSLRs allowing 3D photography. It was accomplished by sweeping the camera horizontally or vertically in Sweep Panorama 3D mode. The picture could be saved as ultra-wide panoramic image or as 16:9 3D photography to be viewed on BRAVIA 3D television setSony VAIO VGN-FZ28 Battery<o:p>

 [edit]History<o:p>

<o:p> 

On August 25, 1981 Sony unveiled a prototype of the first still video camera, the Sony Mavica. This camera was an analog electronic camera that featured interchangeable lenses and a SLR viewfinder.<o:p>

At Photokina in 1986, Nikon revealed a prototype analog electronic still SLR camera, the Nikon SVC, a precursor to the digital SLR.[23] The prototype body shared many features with the N8008.[23]<o:p>

In 1991, Kodak released the first commercially available digital SLR, the Kodak DCS-100. It consisted of a modified Nikon F3 SLR body, modified drive unit, and an external storage unit connected via cable. The 1.3 megapixel camera cost approximately US$30,000. This was followed by the Kodak DCS-200 with integrated storage.[24] Sony VAIO VGN-FZ31B Battery<o:p>

<o:p> 

Over the next decade, DSLRs have been released by various companies, including Canon, Nikon, Kodak, Pentax, Olympus, Panasonic, Samsung, Minolta (later Konica Minolta, and whose camera assets were then acquired by Sony), Fujifilm, and Sigma, with higher resolutions and lower prices.<o:p>

In 1999, Nikon announced the Nikon D1, the first DSLR to truly compete with, and begin to replace, film cameras in the professional photojournalism and sports photography fields. This camera was able to use current autofocus Nikkor lenses available at that time for the Nikon film series cameras, and was also able to utilize the older Nikon and similar, independent mount lenses designed for those cameras. A combination of price, speed, and image quality was the beginning of the end of 35 mm film for these markets. Sony VAIO VGN-FZ31E Battery<o:p>

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In January 2000, Fujifilm announced the FinePix S1 Pro, the first DSLR marketed to non-professionals.<o:p>

In November 2001, Canon released its 4.1 megapixel EOS-1D, the brand's first professional digital body.<o:p>

In 2003, Canon introduced the 6.3 megapixel EOS 300D SLR camera (known in the United States as the Digital Rebel and in Japan as the Kiss Digital) with an MSRP of US$999, directed at the consumer market. Its popularity encouraged other manufacturers to produce affordable digital SLR cameras, lowering entry costs and allowing more amateur photographers to purchase DSLRs.<o:p>

In 2004 Konica Minolta released Konica Minolta Maxxum 7D, first DSLR with in-body image stabilization[25] which later on become standard in Pentax, Olympus and Sony Alpha cameras.<o:p>

In early 2009 Nikon released D90, first DSLR to feature video recording. Since then all major companies offer cameras with this functionality. Sony VAIO VGN-FZ31J Battery<o:p>

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In September 2009 Sony released first sub-2000 USD full frame DSLR, the Sony Alpha 850, creating first accessible full frame camera for amateur photographers.<o:p>

Since then the number of megapixels in imaging sensors have increased steadily, with most companies focusing on, high ISO performance, speed of focus, higher frame rates, the elimination of digital 'noise' produced by the imaging sensor, and price reductions to lure new customers.<o:p>

In November 2010, DSLR cameras were publicly banned in Kuwait, with the Ministry of Information, Ministry of Social Affairs and Ministry of Finance claiming that they should be used for journalistic purposes only.[26] Sony VAIO VGN-FZ31M Battery<o:p>

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[edit]Market share<o:p>

As of 2008, DSLR sales are dominated by Canon's and Nikon's offerings. For 2007, Canon edged out Nikon with 41% of worldwide sales to the latter's 40%, followed by Sony and Olympus each with approximately 6% market share.[27] In the Japanese domestic market, Nikon captured 43.3% to Canon's 39.9%, with Pentax a distant third at 6.3%.[28]<o:p>

The duopoly of Canon and Nikon is sometimes referred to as "Canikon" or "Nikanon" in online forums in skeptical challenge to the presumptive acceptance of these manufacturer's cameras as always "the best". Nevertheless, Canon and Nikon have used their professional market presence especially persuasively in the sale of entry level offerings. Online contributors often challenge the "Canikon/Nikanon" supposed superiority when they believe there are superior innovations from the smaller DSLR manufacturers. Sony VAIO VGN-FZ32B Battery<o:p>

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The DSLR market is dominated by Japanese companies, including all of the top five manufacturers (Canon, Nikon, Olympus, Pentax, and Sony), as well as Fujifilm, Mamiya, Panasonic, and Sigma. Leica is German, Hasselblad is Swedish, and Samsung is Korean, while the American company Kodak formerly produced DSLRs as well.<o:p>

[edit]Present-day models<o:p>

Mainstream DSLRs (full-frame or smaller image sensor format) are currently produced by Canon, Fujifilm, Leica, Nikon, Olympus, Panasonic, Pentax, Samsung, Sigma, and Sony. Phase One, Leaf, Linhof, Hasselblad and Mamiya, amongst others, produce expensive, high-end medium-format view-cameras.<o:p>

Canon's current EOS digital line includes the 1000D,[29] 450D,[29] 50D, 5D Mark II, and the 1Ds Mark III. Canon's latest cameras, the 500D, 7D, and 1D Mark IV were introduced in 2009, while the 550D and 60D were introduced in 2010. As of January 2010, all current Canon DSLRs use CMOS sensors. Sony VAIO VGN-FZ37 Battery<o:p>

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Fujifilm currently sells the Fujifilm FinePix S5 Pro DSLR, compatible with the Nikon F-mount lens system. It is based on the Nikon D200 camera body, but utilizes Fuji's sensor technology (Fujifilm SuperCCD SR Pro) and menu system. Fuji previously offered the Fujifilm FinePix IS Pro, which has the unique ability to capture light in the infrared and ultraviolet spectrums.<o:p>

Nikon also has a broad line of DSLRs currently including the D3100, D5000, D90, D7000, D300S, D700, D3S and the D3X. The D3, announced in August 2007, is the company's first full-frame digital SLR.[30] Sony VAIO VGN-FZ51B Battery<o:p>

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Olympus makes DSLR cameras and lenses as part of the Four Thirds System. Current Olympus models include the E-620, E-30 and E-3. Unique features include a smaller size, an effective sensor dust reduction system, and in-body image stabilization, along with a crop factor of 2 (compared to 1.6 in most DSLR's) and an aspect ratio of 4:3 (instead of 3:2). Four Thirds lenses are especially highly regarded.[31][32]<o:p>

<o:p> 

<o:p> 

Pentax K-7<o:p>

Pentax (in collaboration with Samsung) currently offers the Pentax K-7, Pentax K-x, Pentax K-m[33], Pentax K200D, and K20D, while Samsung offers the Samsung GX-20, a clone of the K20D, and the GX-10, a clone of the now-discontinued Pentax K10D. Innovative features include in-body image stabilization, dust reduction system, use of standard AA batteries in the K200D and K-m, weather-proof sealing (first introduced on the K10D, and otherwise found only in more expensive semi-pro models like the Nikon D200), and adoption of Adobe's DNG standard raw image format. Also, they offer extensive backwards compatibility, accepting all Pentax K mount lenses made since 1975 (though the automatic light metering functionality of some early lenses does not work). Sony VAIO VGN-FZ52B Battery<o:p>

<o:p> 

Sigma produces DSLRs using the Foveon X3 sensor, rather than the conventional Bayer sensor. This is claimed to give higher colour resolution although headline pixel counts are lower than conventional Bayer-sensor cameras. Their current model is the Sigma SD14. Sigma is the only DSLR manufacturer which sells lenses for other brands' lens mounts. Sony VAIO VGN-FZ61B Battery<o:p>

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Currently Sony offer is focused mostly on Entry-level and Midrange cameras, with addition of two professional full-frame DSLRs: α900 and α850. Entry level offer is made of two cameras: Sony Alpha 290 without Live View and Sony Alpha 390 with it, and tiltable LCD. Midrange cameras are Sony Alpha 450, cheap, classic DSLR without Quick AF Live View, though bigger viewfinder, Sony Alpha 560 and Sony Alpha 580 featuring video recording, 3D photography and set of more advanced functions, and finally Sony Alpha 33 and Sony Alpha 55 featuring full time phase detection autofocus during video recording as well as continious shooting of up to 10 fps. The α series offers in-body sensor-shift image stabilization and retains the Minolta AF lens mount.<o:p>

Hasselblad, Linhof, Leaf, Mamiya and Phase One, amongst others, produce medium format-sized (6x4.5 cm., 6x6cm.) view-cameras, which produce high resolution digital images. Their sensors (over 60 megapixel in some cases) are able to capture much more detail than the full-frame and smaller sensors found in DSLR cameras. Sony VAIO VGN-FZ62B Battery<o:p>

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[edit]DSLRs compared to other digital cameras<o:p>

<o:p> 

[edit]Fixed-lens cameras<o:p>

Non-SLR digital cameras generally fall into two types: compact digicams, and SLR-like bridge digital cameras (also known as advanced digital cameras) which offer larger zoom ranges, better optics, and more manual controls. Both types have permanently fixed lenses. While the only defining feature of an SLR is its reflex viewfinder system, extant digital SLR models generally offer the following advantages over fixed-lens cameras of the same generation:<o:p>

Choice of interchangeable[34] (and often higher-quality) lenses. Sony VAIO VGN-FZ72B Battery<o:p>

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Image sensors of much larger size and often higher quality, offering lower noise,[35] which is useful in low light, and greater dynamic range.[36]<o:p>

Optical viewfinders which tend to be more comfortable and efficient, especially for action photography and in low-light conditions.<o:p>

DSLRs often offer faster and more responsive performance, with less shutter lag, faster autofocus systems, and faster frame rates.[37]<o:p>

The larger focal length for the same field of view allows creative use of depth of field effects.[38]<o:p>

Ability to attach additional accessories[39] including hot shoe-mounted flash units, battery grips for additional power and hand positions, external light meters, and remote controls<o:p>

There are also certain drawbacks to current DSLR designs, compared to fixed-lens cameras:<o:p>

Generally greater size and weight.[40] Sony VAIO VGN-FZ90HS Battery<o:p>

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Generally greater cost.[40]<o:p>

Few DSLRs with a video mode.[40] With the exception of cameras such as the Canon EOS 550D, Canon EOS 7D, Nikon D90, Nikon D7000, Nikon D3s and the Canon EOS 5D Mark II[41], few DSLRs produced so far can record full-motion video, while this has become a standard feature of compact digital cameras.<o:p>

Louder operation, due to the SLR mirror mechanism.[42]<o:p>

Potential contamination of the sensor by dust particles, when the lens is changed (though recent dust reduction systems alleviate this).<o:p>

Small digicams generally can focus better on closer objects than typical DSLR lenses.[43]<o:p>

[edit]SLR-like cameras – "bridge cameras"<o:p>

Main article: Bridge digital camera<o:p>

The "SLR-like" or "advanced" digicams offer a non-optical electronic through-the-lens (TTL) view through the focusing lens, via the eye-level electronic viewfinder (EVF) as well as the rear LCD. The difference in views compared to a DSLR is that the EVF shows a digitally-created TTL image, whereas the viewfinder in a DSLR shows an actual optical TTL image via the reflex viewing system. An EVF image has lag time (that is, it reacts with a delay to view changes and has a lower resolution than an optical viewfinder) but achieves parallax-free viewing using less bulk and mechanical complexity than a DSLR with its reflex viewing system. Sony VAIO VGN-FZ490EAB Battery<o:p>

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Windows Mobile

Windows Mobile is a mobile operating system developed by Microsoft that was for use in smartphones and mobile devices, but is being phased out to specialized markets.[2]<o:p>

The current version is called "Windows Mobile 6.5". It is based on the Windows CE 5.2 kernel, and features a suite of basic applications developed using the Microsoft Windows API. It is designed to be somewhat similar to desktop versions of Windows, feature-wise and aesthetically. Additionally, third-party software development is available for Windows Mobile, and software applications can be purchased via the Windows Marketplace for Mobile. Kingston HyperX-KHX1333C7D3K2/2G<o:p>

Originally appearing as the Pocket PC 2000 operating system, most Windows Mobile devices come with a stylus pen, which is used to enter commands by tapping it on the screen.[3] Microsoft announced a completely new phone platform, Windows Phone 7, at the Mobile World Congress in Barcelona on February 15, 2010. Phones running Windows Mobile 6.x will not be upgradeable to version 7.[4] Kingston DDR3-KHX1333C7D3K2/4G<o:p>

Windows Mobile's share of the Smartphone market has fallen year-on-year,[5] decreasing 20% in Q3 2009.[6] It is the 5th most popular smartphone operating system, with a 5% share of the worldwide smartphone market (after Symbian, BlackBerry OS, Android and iPhone).[7] In the United States, it is the 3rd most popular smartphone operating system for business use (after BlackBerry OS and iPhone), with a 24% share among enterprise users.[8] Microsoft is phasing out Windows Mobile to specialized markets, such as rugged devices, and focusing on its new mobile platform, Windows Phone 7.[2]<o:p>

Windows Mobile for Pocket PC carries these standard features in most of its versions:<o:p>

Today Screen shows the current date, owner information, upcoming appointments, e-mail messages, and tasks. (Is now Home screen in later WM6.5 builds)<o:p>

The taskbar shows the current time and the volume. Kingston DDR3 1600mhz 4GB<o:p>

Office Mobile a suite of Mobile versions of Microsoft Office applications<o:p>

Outlook Mobile comes with Windows Mobile.<o:p>

Internet Explorer Mobile is an Internet browser developed by Microsoft for Pocket PC and Handheld PC that comes loaded by default with Windows Mobile and Windows CE for Handheld PC.<o:p>

Windows Media Player for Windows Mobile.<o:p>

Client for PPTP VPNs.<o:p>

Internet Connection Sharing (ICS) which in mobile phones allows attached computers to share internet connections via USB and Bluetooth.<o:p>

Coherent file system similar to that of Windows 9x/Windows NT and support for many of the same file types.<o:p>

Ability to multitask.<o:p>

[edit]Hardware<o:p>

See also: List of Windows Mobile devices<o:p>

There are three versions of Windows Mobile for various hardware devices:[9]<o:p>

Windows Mobile Professional runs on (smartphones) with touchscreens<o:p>

Windows Mobile Standard runs on phones with regular screens<o:p>

Windows Mobile Classic which runs on 'Windows Mobile Classic devices' (Pocket PCs). Kingston DDR3 1600mhz 2gb<o:p>

An O2 Pocket PC phone<o:p>

A Smartphone (T-Mobile Dash)<o:p>

[edit]Windows Mobile Classic devices (Pocket PC)<o:p>

Main article: Pocket PC<o:p>

A 'Windows Mobile Classic device' is a Windows Mobile personal digital assistant (PDA) that does not have telephone functionality. It was formerly known as the Pocket PC. It was the original intended platform for the Windows Mobile operating system. These devices consisted of both standalone Pocket PC devices without mobile phone capabilities, and those that included mobile phone capabilities. The most current name of Windows Mobile intended for use on Pocket PCs is officially "Windows Mobile 6 Professional" for devices with mobile phone capabilities and "Windows Mobile 6 Classic" for devices without mobile phone capabilities. Kingston DDR3 1800mhz 4gb <o:p>

[edit]Windows Mobile Smartphones<o:p>

Main article: Smartphone<o:p>

The 'Windows Mobile' (Microsoft's term for its range of smartphones) became the next hardware platform after the Pocket PC to run Windows Mobile, and debuted with the release of Pocket PC 2002. Although in the broad sense of the term "Smartphone", both Pocket PC phones and Microsoft branded Smartphones each fit into this category, it should be noted that Microsoft's use of the term "Smartphone" includes only more specific hardware devices that differ from Pocket PC phones. Such Smartphones were originally designed without touchscreens, intended to be operated more efficiently with only one hand, and typically had lower display resolution than Pocket PCs. Microsoft's focus for the Smartphone platform was to create a device that functioned well as a phone and data device in a more integrated manner.[10] Kingston DDR3 1800mhz 2gb<o:p>

 [edit]Pocket PC 2000<o:p>

Typical Pocket PC 2000 Today Screen.<o:p>

Pocket PC 2000, originally codenamed "Rapier",[11] was released on April 19, 2000, and was based on Windows CE 3.0. It was the debut of what was later dubbed the Windows Mobile operating system, and meant to be a successor to the operating system aboard Palm-Size PCs. Backwards compatibility was retained with such Palm-Size PC applications. Pocket PC 2000 was intended mainly for Pocket PC devices, however several Palm-Size PC devices had the ability to be updated as well. In addition, several Pocket PC 2000 phones were released, however Microsoft's "Smartphone" hardware platform was not yet created. The only resolution supported by this release was 240 x 320 (QVGA). Removable storage card formats that were supported were CompactFlash and MultiMediaCard. At this time Pocket PC devices had not been standardized with a specific CPU architecture. As a result, Pocket PC 2000 was released on multiple CPU architectures; SH-3, MIPS, and ARM. Kingston DDR3 1333C7D3K2/4G<o:p>

Aesthetically, the original Pocket PC operating system was similar to Windows 98, Windows Me, and Windows 2000 operating systems.<o:p>

Features/built-in applications for Pocket PC 2000 included the following:[12]<o:p>

Typical Pocket PC 2002 Today Screen.<o:p>

Pocket PC 2002, originally codenamed "Merlin",[11] was released in October 2001. Like Pocket PC 2000, it was powered by Windows CE 3.0. Although targeted mainly for 240 × 320 (QVGA) Pocket PC devices, Pocket PC 2002 was also used for Pocket PC phones, and for the first time, Smartphones.[13] These Pocket PC 2002 Smartphones were mainly GSM devices. With future releases, the Pocket PC and Smartphone lines would increasingly collide as the licensing terms were relaxed allowing OEMs to take advantage of more innovative, individual design ideas. Aesthetically, Pocket PC 2002 was meant to be similar in design to the then newly released Windows XP. King ddr 3 KHX1333C7D3K2/2GX<o:p>

New features/built-in applications included the following:[<o:p>

Spell checker and Word count tool in Pocket Word<o:p>

Savable downloads and WAP in Pocket Internet Explorer<o:p>

Virtual Private Networking support<o:p>

Synchronization of folders<o:p>

MSN Messenger<o:p>

Terminal Services<o:p>

Windows Media Player 8 with streaming capability<o:p>

Microsoft Reader 2<o:p>

Palm OS support for file beaming<o:p>

Improved Pocket Outlook<o:p>

Digital rights management (DRM) support in Microsoft ReaderKINGSTON DDR3 KHX1600C7D3K2/4GX<o:p>

[edit]Windows Mobile 2003<o:p>

Typical Windows Mobile 2003 for Pocket PC Today Screen<o:p>

Windows Mobile 2003 (aka wm2003 and WM2003), originally codenamed "Ozone",[11] was released on June 23, 2003, and was the first release under the Windows Mobile banner. It came in four editions: "Windows Mobile 2003 for Pocket PC Premium Edition", "Windows Mobile 2003 for Pocket PC Professional Edition", "Windows Mobile 2003 for Smartphone" and "Windows Mobile 2003 for Pocket PC Phone Edition". The last was designed especially for Pocket PCs which include phone functionalities. The Professional Edition was used in Pocket PC budget models. It lacked a number of features that were in the Premium Edition, such as a client for L2TP/IPsec VPNs. Windows Mobile 2003 was powered by Windows CE 4.20. KINGSTON DDR3 KHX1600C7D3K2/4G<o:p>

New features/built-in applications included the following:[18]<o:p>

Support for add-on keyboards<o:p>

Enhanced communications interface with Bluetooth device management<o:p>

Bluetooth file beaming support<o:p>

Bluetooth headset support<o:p>

Pictures application with viewing, cropping, e-mail, and beaming support<o:p>

Jawbreaker game<o:p>

Enhanced Pocket Outlook with vCard and vCal support<o:p>

Improved Pocket Internet Explorer<o:p>

Windows Media Player 9.0 with streaming optimization<o:p>

SMS reply options for Phone Edition<o:p>

MIDI file support as ringtones in Phone Edition<o:p>

[edit]Windows Mobile 2003 SE<o:p>

Windows Mobile 2003 Second Edition, also known as "Windows Mobile 2003 SE", was released on March 24, 2004 and first offered on the Dell Axim x30. This was the last version which allowed users to backup and restore an entire device through ActiveSync. KINGSTON DDR3 KHX1333C9D3K2/4G<o:p>

New features/built-in applications included the following:<o:p>

Portrait and Landscape switching for Pocket PCs<o:p>

Single-Column layout in Pocket Internet Explorer<o:p>

VGA (640×480), 176 220, 240x240, 480x480 Screen resolution<o:p>

Wi-Fi Protected Access (WPA) support<o:p>

[edit]Windows Mobile 5<o:p>

Typical Windows Mobile 5.0 for Pocket PC Today Screen<o:p>

Windows Mobile 5.0, originally codenamed "Magneto",[11] was released at Microsoft's Mobile and Embedded Developers Conference 2005 in Las Vegas, May 9–May 12, 2005. Microsoft plans to offer mainstream support for Windows Mobile 5 through October 12, 2010, and extended support through October 13, 2015.[19] It was first offered on the Dell Axim x51. It used the .NET Compact Framework 1.0 SP3 — an environment for programs based on .NET. KINGSTON DDR3 KHX1333C9D3K2/2G<o:p>

Windows Mobile 5.0 included Microsoft Exchange Server "push" functionality improvements that worked with Exchange 2003 SP2.[20] The "push" functionality also required vendor/device support[21] With AKU2 software upgrades all WM 5.0 devices supported DirectPush.<o:p>

WM 5.0 featured increased battery life due to Persistent storage capability. Previously up to 50% (enough for 72 hours of storage) of battery power was reserved just to maintain data in volatile RAM. This continued the trend of Windows-based devices moving from using RAM as their primary storage medium to the use of a combination of RAM and flash memory (in use, there's no distinction between the two apparent to the user). Programs and frequently accessed data run in RAM, while most storage is in the flash memory. The OS seamlessly moves data between the two as needed. Everything is backed up in the flash memory, so unlike previous devices, WM5 devices do not lose any data if power is lost. KINGSTON DDR3 KHX1333C7D3k3/6GX<o:p>

With Windows Mobile 5.0, OS updates were released as Adaptation kit upgrades. AKU 3.5 is the most recent release for WM 5.0.<o:p>

Further new features and built-in applications included:<o:p>

New version of Office called "Office Mobile"<o:p>

PowerPoint Mobile<o:p>

Graphing capability in Excel Mobile<o:p>

Tables and graphics insertion in Word Mobile<o:p>

Windows Media Player 10 Mobile<o:p>

Photo Caller ID<o:p>

DirectShow support<o:p>

Picture and Video package, which converged the management of videos and pictures<o:p>

Enhanced Bluetooth support<o:p>

Global Positioning System (GPS) management interfaceKINGSTON DDR3 KHX1333C7D3k3/3GX<o:p>

Default QWERTY keyboard-support<o:p>

Error reporting facility similar to that present in desktop and server Windows systems<o:p>

ActiveSync 4.2 with 15% increased synchronization speed<o:p>

[edit]Windows Mobile 6<o:p>

Windows Mobile 6.1 Standard Today Screen<o:p>

Windows Mobile 6, formerly codenamed "Crossbow",[11] was released on February 12, 2007[22] at the 3GSM World Congress 2007. It comes in three different versions: "Windows Mobile 6 Standard" for Smartphones (phones without touchscreens), "Windows Mobile 6 Professional" for Pocket PCs with phone functionality, and "Windows Mobile 6 Classic" for Pocket PCs without cellular radios.[23]<o:p>

Windows Mobile 6 is powered by Windows CE 5.0 (version 5.2) and is strongly linked to Windows Live and Exchange 2007 products. Windows Mobile 6 Standard was first offered on the Orange's SPV E650,[24] while Windows Mobile 6 Professional was first offered on the O2's Xda Terra.[25] Aesthetically, Windows Mobile 6 was meant to be similar in design to the then newly released Windows Vista. Functionally, it works much like Windows Mobile 5, but with much better stability. KINGSTON DDR3 KHX1600C7D3K3/6GX<o:p>

New features/built-in applications include the following:[26]<o:p>

320x320 and 800x480 (WVGA) screen resolution support (The S01SH or "Em One" by Sharp was the first and only device to have a 800x480 screen on WM5)[27]<o:p>

Office Mobile support for Smartphones<o:p>

Operating System Live Update[28]<o:p>

Improved Remote Desktop access[29] (Available for only certain Pocket PCs)[30]<o:p>

VoIP (Internet calling) support with AEC (Acoustic Echo Cancelling) and MSRT Audio Codec<o:p>

Windows Live for Windows Mobile[31]<o:p>

Customer Feedback option[32]<o:p>

Enhanced Microsoft Bluetooth Stack<o:p>

Storage Card Encryption (encryption keys are lost if device is cold-booted).<o:p>

Smartfilter for searching within programs<o:p>

Improved Internet Sharing<o:p>

HTML email support in Outlook Mobile<o:p>

Search ability for contacts in an Exchange Server Address Book<o:p>

AJAX, JavaScript, and XMLDOM support on Internet Explorer Mobile<o:p>

Out of Office Replies with Microsoft Exchange 2007<o:p>

Unlicensed Mobile Access (UMA) support for select operators<o:p>

Server Search on Microsoft Exchange 2007<o:p>

.NET Compact Framework v2 SP2 Preinstalled in ROM<o:p>

Microsoft SQL Server 2005 Compact Edition Preinstalled in ROM<o:p>

OneNote Mobile as a companion to Microsoft Office OneNote<o:p>

Office Mobile 6.1 announced[33] with support for Office 2007 document formats (pptx, docx, xlsx).<o:p>

[edit]Windows Mobile 6.1<o:p>

Windows Mobile 6.1 Professional Today ScreenKINGSTON DDR3 KHX1600C8D3K3/6GX)<o:p>

Windows Mobile 6.1 was announced April 1, 2008. It is a minor upgrade to the existing Windows Mobile 6 platform which brings with it various performance enhancements, a redesigned Home screen featuring horizontal tiles that expand on clicking to display more information, although this new home screen is featured only on Windows Mobile Standard edition. This feature was inexplicably left out of the Professional edition.[34] Several other changes such as threaded SMS, full page zooming in Internet Explorer and 'Domain Enroll' have also been added, along with a "mobile" version of the Microsoft OneNote program and an interactive "Getting Started" wizard. Domain Enroll is functionality to connect the device to System Center Mobile Device Manager 2008, a product to manage mobile devices.[35] There are other differences as well. kingston laptop DDR2(667)  1GBThe most prominent difference for the user is that the Standard version (like earlier versions) still creates automatic links for telephone numbers in Tasks and Appointments, which allows for the easier click and dial of stored telephone numbers within these Outlook items. For some reason, the Professional version has eliminated this important feature. Windows Mobile 6.1 also featured improved bandwidth efficiency in its push-email protocol "Activesync" of "up to 40%",[36] this reduced data usage was the cause of considerably improved battery life in many devices. kingston laptop  DDR2(667)  2GB<o:p>

Aside from the visual and feature distinctions, the underlying CE versions can be used to differentiate WM6.0 from WM 6.1. The version of Windows CE in WM 6.0 is 5.2.*, with the final number being a 4 digit build ID (e.g. 5.2.1622 on HTC Wing). In WM 6.1, the CE version is 5.2.* with a 5 digit build number (e.g. 5.2.19216 on Palm Treo 800w).<o:p>

[edit]Windows Mobile 6.5<o:p>

A screenshot of the Windows Mobile 6.5 Today Screen, 'Titanium'<o:p>

Windows Mobile 6.5 was never part of Microsoft's mobile phone roadmap, and has been described by its chief executive, Steve Ballmer, as "not the full release [Microsoft] wanted" until the multi-touch enabled Windows Mobile 7 (now replaced by Windows Phone 7) arrives in 2010.[37] Version 6.5 is an upgrade to Windows Mobile 6.1 that was released to manufacturers on May 11, 2009, and the first devices running the operating system debuted in late October '09.[38] This incremental update includes some significant new added features, such as a revamped GUI, new today screen with vertically scrollable labels (called 'Titanium'); though is generally regarded as a minor upgrade.[39] It also includes the new Internet Explorer Mobile 6 browser, which has an improved interface over previous versions.[40] kingston laptop DDR2(800)  1GB<o:p>

Microsoft unveiled this version at the 2009 Mobile World Congress in February,[41] and several devices now run this Windows Mobile version,[42] those devices running Windows Mobile 6.5 onwards are marketed as "Windows phones". Along with Windows Mobile 6.5, Microsoft announced several Cloud computing services codenamed "SkyBox","SkyLine","SkyMarket".[43] "SkyBox" has been confirmed as My Phone,[44] while "SkyMarket" has been confirmed as Windows Marketplace for Mobile.[45] Some aspects of the user interface have been redesigned with the home screen resembling that of Microsoft's Zune player and the sliding panel interface of Windows Mobile 6.1 Standard. This version was designed mainly for easier finger usage.[46][47] Whilst this version of Windows Mobile does not natively support capacitive screens, mobile manufacturers have been able to successfully implement it on their devices [48]<o:p>

Several phones currently running Windows Mobile 6.1 are updatable to Windows Mobile 6.5.[49]<o:p>

[edit]Windows Mobile 6.5.1kingston laptop -DDR2(800)-2GB<o:p>

Builds of Windows Mobile 6.5.1 have been unofficially ported to several Windows Mobile phones.[50] Windows Mobile 6.5.1 brings a more finger-friendly user interface,[51] including icon based soft buttons (rather than text based),[52] an updated contacts app,[53] Microsoft (rather than the mobile carrier) support for A-GPS,[51] improved threaded text messaging,[54] and performance improvements.[55]<o:p>

[edit]Windows Mobile 6.5.3<o:p>

A Screenshot of the Windows Phone 6.5.3 Today Screen 'Titanium' (notice the new location of the start button)<o:p>

On February 2, 2010, the Sony Ericsson Aspen with Windows Mobile 6.5.3 was officially announced, making it the first Windows Phone 6.5.3 smartphone.[56] Since November 2009, several 6.5.3 builds had leaked (28nnn) and had been unofficially ported to some Windows Phones. kingsto laptop DDR3(1066)  1GB<o:p>

Windows Mobile 6.5.3 brings a more finger-friendly user interface with several new ease of use features such as support for multitouch, complete touch control i.e. no need for a stylus, and drag and drop start menu icons. Touchable tiles now replace soft keys."[57] Internet Explorer Mobile 6 has also received some major updates including decreased page load time, improved memory management and gesture smoothing.[58]<o:p>

Additional features of newer Windows Mobile 6.5.3 builds include threaded email and Office Mobile 2010.[58] kingston-Laptop-DDR3(1066)-2GB<o:p>

[edit]Windows Mobile 6.5.5<o:p>

Several builds of Windows Mobile 6.5.x have leaked since January 2010 and have been unofficially ported to some Windows Mobile phones.[59] The name Windows Mobile 6.5.5 has been applied to these newer builds. However, this naming scheme remains unconfirmed by Microsoft.<o:p>

[edit]Successor to Windows Mobile<o:p>

[edit]Windows Phone 7<o:p>

Main article: Windows Phone 7<o:p>

The Start screen of Windows Phone 7<o:p>

Windows Phone 7 was launched in Europe, Singapore and Australia on October 21, 2010, and in the US & Canada on November 8, 2010, while rest of the world to follow in 2011.[60] Microsoft had originally planned to continue the Windows Mobile line to Windows Mobile 7, based on an upgrade to the Windows Mobile platform, codenamed Photon. The original Photon and Windows Mobile 7 have since been scrapped, however, Microsoft decided to create a new mobile OS platform and officially announced Windows Phone 7 Series in its place.[61] Microsoft has since renamed the operating system from Windows Phone 7 Series to Windows Phone 7.[62] kingston-Laptop-DDR3(1333)-1GB)<o:p>

Windows Phone 7 was initially intended to be released during 2009, but several delays, likely due to the move away from Photon and to building an entirely different and new platform, prompted Microsoft to develop Windows Mobile 6.5 as an interim release. During the Mobile World Congress 2010 in Barcelona, Microsoft revealed details of Windows Phone 7, which features a new operating system and integration with Xbox Live and Zune services.[63]<o:p>

Phones currently running Windows Mobile 6.x are not upgradeable to Windows Phone 7.[64]<o:p>

[edit]Microsoft Kin<o:p>

Main article: Microsoft Kin<o:p>

Microsoft Kin evolved from Microsoft's purchase of Danger Hiptop in 2008.[65] Details are scarce, but a ZDNet source said that Microsoft Kin brings an entirely new software stack and services.[66] Some reports say that the new mobile phone platform is based around the Zune media device.[67] kingston Laptop DDR3(1333) 2GB<o:p>

Microsoft Kin was developed inside Microsoft's Premium Mobile Experiences (PMX) division.[68] Microsoft brought in employees from Danger Inc., with the intention of infusing industry talent and mobile experience into the project. The goal was said to be to create a mobile platform far superior to that of the Danger Sidekick. Reports say that Microsoft Kin was originally going to be based on Windows Phone 7. However, due to delays with the latter, it was built directly upon Windows CE. It will feature the Zune marketplace, and uses XNA as a game platform.[68] kingston DDR2(667) 1GB<o:p>

The platform was aimed at producing phones designed for users who are heavily into social networking and instant messaging.[69] The technology acquired from Danger Hiptop has been described as a family of mobile devices running a bespoke operating system as part of a client–server system that is then licenced to mobile carriers.[70]<o:p>

Microsoft debuted two new handsets based on Microsoft Kin, codenamed Turtle and Pure, possibly to debut at the Consumer Electronics Show.[71] The Microsoft designed phones were manufactured by Sharp and co-branded.[72] According to the MobileTechWorld website, Microsoft Kin is a software service running on top of Windows Phone 7 devices.[73] Microsoft announced the discontinuation of the KIN line on June 30, 2010, only six weeks after it was launched.[74] wd passport essential 500GB white<o:p>

A Ford Territory with Windows Mobile advertising seen in Auckland, New Zealand in 2008.<o:p>

Windows Mobile's share of the smartphone market has been in decline year-on-year. Gartner research data showed that while the total smartphone industry grew 27% between 2008 and 2009, Windows Mobile's share of the smartphone market fell 2.7% in that same period.[5]<o:p>

In 2004, Windows Mobile accounted for 23% of worldwide smartphone sales.[75] Windows Mobile was projected to overtake Symbian to become the leading mobile OS by 2010.[76] But by 2008, its share had dropped to 14%.[77] Microsoft licensed Windows Mobile to four out of the world's five largest mobile phone manufacturers, with Nokia being the exception.[78] wd passport essential 500GB black<o:p>

Although Microsoft apparently has 50 handset partners,[79] 80% of the 50 million Windows Mobile devices made have been built by one contract manufacturing group, HTC, which makes handsets for several major companies under their brands, as well as under its own brand.[80]<o:p>

In February 2009 Microsoft signed a deal with the third largest mobile phone maker, LG Electronics, to license Windows Mobile OS on 50 upcoming LG smartphone models.[81] But in September, 2009, Palm, Inc. announced it would drop Windows Mobile from its smartphone line-up.[82] An October 2009 report in DigiTimes said that Acer will shift its focus from Windows Mobile to Google Android.[83] wd passport essential 500GB red<o:p>

Windows Mobile used to be the most popular handset for business use, but 2009 saw this position depreciate. An InformationWeek survey found that 24% of planned business deployments of mobile application were for Windows Mobile, putting it in 3rd place, behind Blackberry (61%) and iPhone (27%).[8]<o:p>

In October, 2009, Gartner predicted that by 2012, Windows Mobile will remain the 4th most popular smartphone platform during the rise of Android only due to BlackBerry falling from 2nd to 5th.[84] The New York Times said that cellular telephone manufacturers are moving away from Windows Mobile, and instead shifting towards Android and Microsoft's new mobile platform, Windows Phone 7.[85] Taiwan's Intelligence & Consulting Institute (MIC) predicted that Android's popularity may force Microsoft to reduce the Windows Mobile licensing fees it charges handset makers, in order to reduce further market share losses.[86] wd passport essential 500GB BLUE<o:p>

Windows Mobile's loss of market share became more rapid in Q3 2009. It suffered a 20% drop in Q3 compared to the previous quarter, at a time when total smartphone sales with all operating systems rose 13%. Gartner estimated that in Q3, 2009, Windows Mobile share of worldwide smartphone sales was 7.9%.[6]<o:p>

Samsung announced in November 2009 that it will phase out the Windows Mobile platform,[87] to concentrate on its own Bada operating system, as well as Google's Android and Microsoft's new mobile platform, Windows Phone 7.[88] wd Passport Essential SE 1TB USB 3.0<o:p>

[edit]Possible trends<o:p>

In late 2009, many industry analysts and media reports began to express concerns about the future viability of the Windows Mobile platform, and whether Microsoft will keep supporting it into the future.<o:p>

ZDnet said that "for all practical purposes, Windows Mobile is a dead platform",[89] while CNET said "Windows Mobile has now been relegated resolutely to has-been status."[90]<o:p>

ABI Research said: "Heading into 2010, the momentum (for Windows Mobile) has dissipated."[91] wd Passport Essential SE 1TB USB 3.0 RED<o:p>

Gartner analysts questioned whether Windows Mobile had a future beyond version 7, due to its poor performance and falling market share. However, Gartner said that while Windows Mobile may be discontinued for consumer-focused smartphones, it still had a future in specialized industrial applications, such as for ruggedized devices used in warehousing and delivery trucks.[91] Gartner said that Windows Mobile 7 could be "the last throw of the dice."[92]<o:p>

Analysts J.Gold Associates said in BusinessWeek that Microsoft will likely exit the mobile operating system market sometime between 2010 and 2011, saying "There are better ways for Microsoft to make money from smartphones than to keep investing in a mobile operating system that's losing share and relevance."[93] wd Passport Essential SE 1TB USB 3.0 blue<o:p>

The New York Times reported that Windows Mobile "is foundering", as cellphone makers desert it in favor of Google's Android phone platform.[85] It cited the difficulties in Microsoft's business model, which involves charging handset manufacturers up to $25 for each copy of Windows Mobile, while rival Google gives away Android for free.[94]<o:p>

The Washington Post said Windows Mobile is "bleeding market share in the space, and the future looks grim." It said that Google is using Android to "kill" Windows Mobile.[95]<o:p>

In February 2010 Microsoft announced a new mobile operating system platform: Windows Phone 7. It has been built from scratch and bears no resemblance to its predecessors. It was released on October 21, 2010 in Europe and on November 8, 2010 in the United States. wd Passport Essential SE 1TB USB 3.0 sliver<o:p>

[edit]Software development<o:p>

See also: Windows Marketplace for Mobile<o:p>

Third-party software development is available for the Windows Mobile operating system. There are several options for developers to use when deploying a mobile application. This includes writing native code with Visual C++, writing Managed code that works with the .NET Compact Framework, or Server-side code that can be deployed using Internet Explorer Mobile or a mobile client on the user's device. The .NET Compact Framework is actually a subset of the .NET Framework and hence shares many components with software development on desktop clients, application servers, and web servers which have the .NET Framework installed, thus integrating networked computing space (a.k.a. "The Cloud").[96] Seagate freeagent Go 500GB<o:p>

Microsoft typically releases Windows Phone Software Development Kits (SDKs) that work in conjunction with their Visual Studio development environment. These SDKs include emulator images for developers to test and debug their applications while writing them. Microsoft also distributes Visual Studio 2008 / 2005 Professional Editions, and server / database counterparts to students as downloads free of charge via its DreamSpark program.[97] Seagate freeagent Go 500GB Black<o:p>

Developer communities have used the SDK to port later versions of Windows Mobile OS to older devices and making the OS images available for free, thus providing the devices with the current feature set. Microsoft has tolerated this procedure for some time but decided in February 2007 to ask developers to take their OS images off the net, which in turn raised discussions.[98] At the same time Microsoft offered upgrades to Windows Mobile 6 versions to manufacturers for free.[99]<o:p>

Lazarus, Lexico, NS Basic and Basic4ppc provide an alternative development environment; they allow for development on the desktop, which is then downloaded to the device. NS Basic and Basic4ppc[100] allow for development on the actual device itself. Seagate freeagent Go 500GB Blue<o:p>

Some 3rd party development tools such as Basic4ppc use the .NET Compact Framework. This has been possible only for the last couple years. Prior to the release of Windows Mobile 2003, third-party software was developed using Microsoft's eMbedded Visual Tools, eMbedded Visual Basic (eVB) and eMbedded Visual C (eVC).[101] eVB programs can usually be converted fairly easily to NS Basic/CE.[102] or to Basic4ppc. Seagate freeagent Goflex 500GB<o:p>

There is also a GCC port called CeGCC. For scripting language, there is a Python port named PythonCE and a Tcl-Tk port called eTcl. It can be used to develop applications on Windows Mobile phone itself.<o:p>

Satellite Forms is a RAD tool that can produce Windows Phone compatible applications that use an RDK runtime engine. Extension libraries extend the functionality for various hardware.<o:p>

On 5 July 2009, Microsoft opened a third-party application distribution service called Windows Marketplace for Mobile.[103]<o:p>

[edit]Criticism<o:p>

This section needs additional citations for verification.<o:p>

Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2010) Seagate freeagent Goflex 500GB red <o:p>

Versions of Windows Mobile prior to 6.5.3 did not recognize multi-touch screens. Device maker HTC Corporation created some work-arounds to allow multi-touch to work on some applications it installed on its HD2 handset. However, Microsoft applications on this handset, such as the Internet Explorer web browser, do not support multi-touch.[104]<o:p>

Windows Mobile does not allow users to view file properties from File Explorer and so a third-party file explorer is needed to remove the "read-only" or "Hidden File" attributes applied to files. Hidden files can be viewed.<o:p>

Windows Mobile does not allow users to view file extensions of unknown file types, although third-party software is available to do this. Seagate freeagent Goflex 500GB silver <o:p>

Windows Mobile devices can easily be used and reset by unauthorised users, such as thieves, as the "Clear Storage" command can be invoked without the need for a password so long as the keypad is not locked and the phone is not turned off, because the CLEAR STORAGE is applied by using embedded, unmodifiable key sequence of "1234" which is also visibly shown in the phone.<o:p>

The interface of Windows Mobile 6.5 shows jarring inconsistencies, with some applications requiring the user to hold a Stylus to make them operate.[105]<o:p>

Many Windows Mobile business applications were designed for a stylus-pen input, and are difficult or impossible to use on a capacitative multi-touch screen.[106] Samsung G2 portable 500GB<o:p>

Unlike Windows for desktop computers, the Windows Mobile operating system cannot be upgraded by the user. Upgrades can only be supplied by telephone service providers or hardware providers. As this requires considerable resource to produce a custom upgrade for each device, generates no income (upgrades have not been chargeable), and extends the life of older equipment instead of encouraging purchase of new, Windows Mobile upgrades are rarely released.[107] However, expert users have developed unofficial, sometimes modified, firmware; this unofficial firmware, or newer Windows Mobile or Phone firmware intended for other devices with the risk of possible incompatibility, can be installed if available with flashing software. Samsung G2 portable green 500GB<o:p>

Several analysts from both Gartner and J.Gold Associates have expressed concern about the long-term future of Windows Mobile.[108] Motorola and Fedex said that Microsoft had given a commitment to continue supporting Windows Mobile, at least for use in rugged industrial devices.[109]<o:p>

On 25 September 2009, Microsoft CEO Steve Ballmer indicated that the company "screwed up with Windows Mobile". He lamented that Windows Mobile version 7 was not yet available. He said he had recently changed the Windows Mobile team to try to recoup losses.[110]<o:p>

Windows Mobile 6.5.x was based on the Windows CE 5.2 kernel, the same kernel that was running in Windows Mobile 5.0 in 2004. Windows Mobile 6.5.x has not been optimized for more modern processors, such as the Snapdragon processors. Its successor, Windows Phone 7, runs an updated kernel based on Windows CE 6 R3 and Windows CE 7.[106] Samsung G2 portable black 500GB<o:p>

A 2009 survey by CFI Group showed that Windows Mobile users had a low level of customer satisfaction when compared to users of other smartphones. Out of a possible 100 points, Windows Mobile rated only 66, compared with BlackBerry (73), Palm Pre (77), Google Android (77), and iPhone (83).[111]<o:p>

 

Operating system

An operating system (OS) is software, consisting of programs and data, that runs on computers and manages the computer hardware and provides common services for efficient execution of various application software.<o:p>

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between application programs and the computer hardware,[1][2] although the application code is usually executed directly by the hardware, but will frequently call the OS or be interrupted by it. Operating systems are found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers. Sony VAIO VGN-FZ11E Battery<o:p>

Examples of popular modern operating systems for personal computers are Microsoft Windows, Mac OS X, and GNU/Linux.[3]<o:p>

Early computers were built to perform a series of single tasks, like a calculator. Operating systems did not exist in their modern and more complex forms until the early 1960s.[4] Some operating system features were developed in the 1950s, such as monitor programs that could automatically run different application programs in succession to speed up processing. Hardware features were added that enabled use of runtime libraries, interrupts, and parallel processing. When personal computers by companies such as Apple Inc., Atari, IBM and Amiga became popular in the 1980s, vendors added operating system features that had previously become widely used on mainframe and mini computers. Later, many features such as graphical user interface were developed specifically for personal computer operating systems. Sony VAIO VGN-FZ11L Battery<o:p>

An operating system consists of many parts. One of the most important components is the kernel, which controls low-level processes that the average user usually cannot see: it controls how memory is read and written, the order in which processes are executed, how information is received and sent by devices like the monitor, keyboard and mouse, and deciding how to interpret information received by networks. The user interface is a component that interacts with the computer user directly, allowing them to control and use programs. The user interface may be graphical with icons and a desktop, or textual, with a command line. Application programming interfaces provide services and code libraries that let applications developers write modular code reusing well defined programming sequences in user space libraries or in the operating system itself. Which features are considered part of the operating system is defined differently in various operating systems. For example, Microsoft Windows considers its user interface to be part of the operating system, while many versions of Linux do not. Sony VAIO VGN-FZ11M Battery<o:p>

History<o:p>

OS/360 was used on most IBM mainframe computers beginning in 1966, including the computers that helped NASA put a man on the moon.<o:p>

Main article: History of operating systems<o:p>

In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer and would arrive at a scheduled time with program and data on punched paper cards and tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a front panel using toggle switches and panel lights. It is said that Alan Turing was a master of this on the early Manchester Mark 1 machine, and he was already deriving the primitive conception of an operating system from the principles of the Universal Turing machine.[citation needed] Sony VAIO VGN-FZ11S Battery<o:p>

Later machines came with libraries of software, which would be linked to a user's program to assist in operations such as input and output and generating computer code from human-readable symbolic code. This was the genesis of the modern-day operating system. However, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a washing line from which tapes were hung with different colored clothes-pegs to indicate job-priority.[citation needed] Sony VAIO VGN-FZ11Z Battery<o:p>

Mainframes<o:p>

For more details on IBM mainframe operating systems, see History of IBM mainframe operating systems.<o:p>

Through the 1950s, many major features were pioneered in the field of operating systems, including batch processing, input/output interrupt, buffering, multitasking, spooling, runtime libraries, link-loading, and programs for sorting records in files. These features were included or not included in application software at the option of application programmers, rather than in a separate operating system used by all applications. In 1959 the SHARE Operating System was released as an integrated utility for the IBM 704, and later in the 709 and 7090 mainframes. Sony VAIO VGN-FZ130E/B Battery<o:p>

During the 1960s, IBM's OS/360 introduced the concept of a single OS spanning an entire product line, which was crucial for the success of the System/360 machines. IBM's current mainframe operating systems are distant descendants of this original system and applications written for OS/360 can still be run on modern machines.[citation needed] In the mid-'70s, MVS, a descendant of OS/360, offered the first[citation needed] implementation of using RAM as a transparent cache for data. Sony VAIO VGN-FZ140E Battery<o:p>

OS/360 also pioneered the concept that the operating system keeps track of all of the system resources that are used, including program and data space allocation in main memory and file space in secondary storage, and file locking during update. When the process is terminated for any reason, all of these resources are re-claimed by the operating system.<o:p>

The alternative CP-67 system for the S/360-67 started a whole line of IBM operating systems focused on the concept of virtual machines. Other operating systems used on IBM S/360 series mainframes included systems developed by IBM: DOS/360 (Disk Operating System), TSS/360 (Time Sharing System), TOS/360 (Tape Operating System), BOS/360 (Basic Operating System), and ACP (Airline Control Program), as well as a few non-IBM systems: MTS (Michigan Terminal System) and MUSIC (Multi-User System for Interactive Computing). Sony VAIO VGN-FZ140E/B Battery<o:p>

Control Data Corporation developed the SCOPE operating system in the 1960s, for batch processing. In cooperation with the University of Minnesota, the KRONOS and later the NOS operating systems were developed during the 1970s, which supported simultaneous batch and timesharing use. Like many commercial timesharing systems, its interface was an extension of the Dartmouth BASIC operating systems, one of the pioneering efforts in timesharing and programming languages. Sony VAIO VGN-FZ140N/B Battery<o:p>

 In the late 1970s, Control Data and the University of Illinois developed the PLATO operating system, which used plasma panel displays and long-distance time sharing networks. Plato was remarkably innovative for its time, featuring real-time chat, and multi-user graphical games. Burroughs Corporation introduced the B5000 in 1961 with the MCP, (Master Control Program) operating system. The B5000 was a stack machine designed to exclusively support high-level languages with no machine language or assembler, and indeed the MCP was the first OS to be written exclusively in a high-level language – ESPOL, a dialect of ALGOL. MCP also introduced many other ground-breaking innovations, such as being the first commercial implementation of virtual memory. During development of the AS400, IBM made an approach to Burroughs to licence MCP to run on the AS400 hardware. This proposal was declined by Burroughs management to protect its existing hardware production. MCP is still in use today in the Unisys ClearPath/MCP line of computers. Sony VAIO VGN-FZ140QE Battery<o:p>

UNIVAC, the first commercial computer manufacturer, produced a series of EXEC operating systems. Like all early main-frame systems, this was a batch-oriented system that managed magnetic drums, disks, card readers and line printers. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the Dartmouth BC system.<o:p>

General Electric and MIT developed General Electric Comprehensive Operating Supervisor (GECOS), which introduced the concept of ringed security privilege levels. After acquisition by Honeywell it was renamed to General Comprehensive Operating System (GCOS). Sony VAIO VGN-FZ15 Battery<o:p>

Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Prior to the widespread use of UNIX, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community.<o:p>

In the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported software to run on more than one system. Early systems had utilized microprogramming to implement features on their systems in order to permit different underlying architecture to appear to be the same as others in a series. In fact most 360's after the 360/40 (except the 360/165 and 360/168) were microprogrammed implementations. But soon other means of achieving application compatibility were proven to be more significant. Sony VAIO VGN-FZ15G Battery<o:p>

The enormous investment in software for these systems made since 1960s caused most of the original computer manufacturers to continue to develop compatible operating systems along with the hardware. The notable supported mainframe operating systems include:<o:p>

 Microcomputers<o:p>

This section does not cite any references or sources.<o:p>

Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2010) Sony VAIO VGN-FZ15T Batter<o:p>

PC-DOS was an early personal computer OS that featured a command line interface.<o:p>

Mac OS by Apple Computers became the first widespread OS to feature a graphical user interface. Many of its features such as windows and icons would later become commonplace in GUIs.<o:p>

The first microcomputers did not have the capacity or need for the elaborate operating systems that had been developed for mainframes and minis; minimalistic operating systems were developed, often loaded from ROM and known as Monitors. One notable early disk-based operating system was CP/M, which was supported on many early microcomputers and was closely imitated in MS-DOS, which became wildly popular as the operating system chosen for the IBM PC (IBM's version of it was called IBM DOS or PC DOS), its successors making Microsoft. In the '80s Apple Computer Inc. (now Apple Inc.) abandoned its popular Apple II series of microcomputers to introduce the Apple Macintosh computer with an innovative Graphical User Interface (GUI) to the Mac OS. Sony VAIO VGN-FZ160E Battery<o:p>

The introduction of the Intel 80386 CPU chip with 32-bit architecture and paging capabilities, provided personal computers with the ability to run multitasking operating systems like those of earlier minicomputers and mainframes. Microsoft responded to this progress by hiring Dave Cutler, who had developed the VMS operating system for Digital Equipment Corporation. He would lead the development of the Windows NT operating system, which continues to serve as the basis for Microsoft's operating systems line. Steve Jobs, a co-founder of Apple Inc., started NeXT Computer Inc., which developed the Unix-like NEXTSTEP operating system. NEXTSTEP would later be acquired by Apple Inc. and used, along with code from FreeBSD as the core of Mac OS X. Sony VAIO VGN-FZ160E/B Battery<o:p>

The GNU project was started by activist and programmer Richard Stallman with the goal of a complete free software replacement to the proprietary UNIX operating system. While the project was highly successful in duplicating the functionality of various parts of UNIX, development of the GNU Hurd kernel proved to be unproductive. In 1991, Finnish computer science student Linus Torvalds, with cooperation from volunteers collaborating over the Internet, released the first version of the Linux kernel. It was soon merged with the GNU user space components and system software to form a complete operating system. Since then, the combination of the two major components has usually been referred to as simply "Linux" by the software industry, a naming convention that Stallman and the Free Software Foundation remain opposed to, preferring the name GNU/Linux. The Berkeley Software Distribution, known as BSD, is the UNIX derivative distributed by the University of California, Berkeley, starting in the 1970s. Freely distributed and ported to many minicomputers, it eventually also gained a following for use on PCs, mainly as FreeBSD, NetBSD and OpenBSD. Sony VAIO VGN-FZ17 Battery<o:p>

Examples of operating systems<o:p>

Microsoft Windows<o:p>

Windows 7, shown here, is the newest release of Windows.<o:p>

Microsoft Windows is a family of proprietary operating systems most commonly used on personal computers. It is the most common family of operating systems for the personal computer, with about 90% of the market share.[5][6][7] Currently, the most widely used version of the Windows family is Windows XP[8], released on October 25, 2001. The newest version is Windows 7 for personal computers and Windows Server 2008 R2 for servers. Sony VAIO VGN-FZ17G Battery<o:p>

Microsoft Windows originated in 1981 as an add-on to the older MS-DOS operating system for the IBM PC. First publicly released in 1985, Windows came to dominate the business world of personal computers, and went on to set a number of industry standards and commonplace applications[POV? – Discuss]. Beginning with Windows XP, all modern versions are based on the Windows NT kernel. Current versions of Windows run on IA-32 and x86-64 processors, although older versions sometimes supported other architectures. Sony VAIO VGN-FZ18 Battery<o:p>

<o:p> 

Windows is also used on servers, supporting applications such as web servers and database servers. In recent years, Microsoft has spent significant marketing and research & development money to demonstrate that Windows is capable of running any enterprise application, which has resulted in consistent price/performance records (see the TPC) and significant acceptance in the enterprise market. However, its usage in servers is not as widespread as personal computers, and here Windows actively competes against Linux and BSD for market share, while still capturing a steady majority by some accounts.[9][10] Sony VAIO VGN-FZ180E Battery<o:p>

edit]Unix and Unix-like operating systems<o:p>

Evolution of Unix systems<o:p>

Main article: Unix<o:p>

Ken Thompson wrote B, mainly based on BCPL, which he used to write Unix, based on his experience in the MULTICS project. B was replaced by C, and Unix developed into a large, complex family of inter-related operating systems which have been influential in every modern operating system (see History). The Unix-like family is a diverse group of operating systems, with several major sub-categories including System V, BSD, and GNU/Linux. The name "UNIX" is a trademark of The Open Group which licenses it for use with any operating system that has been shown to conform to their definitions. "Unix-like" is commonly used to refer to the large set of operating systems which resemble the original Unix. Sony VAIO VGN-FZ180E/B Battery<o:p>

Unix-like systems run on a wide variety of machine architectures. They are used heavily for servers in business, as well as workstations in academic and engineering environments. Free Unix variants, such as GNU/Linux and BSD, are popular in these areas.<o:p>

Some Unix variants like HP's HP-UX and IBM's AIX are designed to run only on that vendor's hardware. Others, such as Solaris, can run on multiple types of hardware, including x86 servers and PCs. Apple's Mac OS X, a hybrid kernel-based BSD variant derived from NeXTSTEP, Mach, and FreeBSD, has replaced Apple's earlier (non-Unix) Mac OS. Sony VAIO VGN-FZ18E Battery<o:p>

Unix interoperability was sought by establishing the POSIX standard. The POSIX standard can be applied to any operating system, although it was originally created for various Unix variants.<o:p>

BSD and its descendants<o:p>

The first server for the World Wide Web ran on NeXTSTEP, based on BSD.<o:p>

Main article: Berkeley Software Distribution<o:p>

A subgroup of the Unix family is the Berkeley Software Distribution family, which includes FreeBSD, NetBSD, and OpenBSD. These operating systems are most commonly found on webservers, although they can also function as a personal computer OS. The Internet owes much of its existence to BSD, as many of the protocols now commonly used by computers to connect, send and receive data over a network were widely implemented and refined in BSD. The world wide web was also first demonstrated on a number of computers running an OS based on BSD called NextStep. Sony VAIO VGN-FZ18G Battery<o:p>

BSD has its roots in Unix. In 1974, University of California, Berkeley installed its first Unix system. Over time, students and staff in the computer science department there began adding new programs to make things easier, such as text editors. When Berkely received new VAX computers in 1978 with Unix installed, the school's undergraduates modified Unix even more in order to take advantage of the computer's hardware possibilities. The Defense Advanced Research Projects Agency of the US Department of Defense took interest, and decided to fund the project. Many schools, corporations, and government organizations took notice and started to use Berkeley's version of Unix instead of the official one distributed by AT&T. Steve Jobs, upon leaving Apple Inc. in 1985, formed NeXT Inc., a company that manufactured high-end computers running on a variation of BSD called NeXTSTEP. One of these computers was used by Tim Berners-Lee as the first webserver to create the World Wide Web. Sony VAIO VGN-FZ18M Battery<o:p>

Developers like Keith Bostic encouraged the project to replace any non-free code that originated with Bell Labs. Once this was done, however, AT&T sued. Eventually, after two years of legal disputes, the BSD project came out ahead and spawned a number of free derivatives, such as FreeBSD and NetBSD. In this two year wait, GNU and Linux appeared.<o:p>

Mac OS X<o:p>

The standard user interface of Mac OS X<o:p>

Main article: Mac OS X<o:p>

Mac OS X is a line of partially proprietary graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers. Mac OS X is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. Unlike its predecessor, Mac OS X is a UNIX operating system built on technology that had been developed at NeXT through the second half of the 1980s and up until Apple purchased the company in early 1997. Sony VAIO VGN-FZ18T Battery<o:p>

The operating system was first released in 1999 as Mac OS X Server 1.0, with a desktop-oriented version (Mac OS X v10.0) following in March 2001. Since then, six more distinct "client" and "server" editions of Mac OS X have been released, the most recent being Mac OS X v10.6, which was first made available on August 28, 2009. Releases of Mac OS X are named after big cats; the current version of Mac OS X is "Snow Leopard".<o:p>

The server edition, Mac OS X Server, is architecturally identical to its desktop counterpart but usually runs on Apple's line of Macintosh server hardware. Mac OS X Server includes work group management and administration software tools that provide simplified access to key network services, including a mail transfer agent, a Samba server, an LDAP server, a domain name server, and others. Sony VAIO VGN-FZ190 Battery<o:p>

Plan 9<o:p>

Ken Thompson, Dennis Ritchie and Douglas McIlroy at Bell Labs designed and developed the C programming language to build the operating system Unix. Programmers at Bell Labs went on to develop Plan 9 and Inferno, which were engineered for modern distributed environments. Plan 9 was designed from the start to be a networked operating system, and had graphics built-in, unlike Unix, which added these features to the design later. It is currently released under the Lucent Public License. Inferno was sold to Vita Nuova Holdings and has been released under a GPL/MIT license. Sony VAIO VGN-FZ190E/1 Battery<o:p>

Linux and GNU<o:p>

Main articles: GNU and Linux<o:p>

<o:p> 

<o:p> 

Ubuntu, a common desktop distribution of Linux<o:p>

Linux is the generic name for a UNIX-like operating system that can be used on a wide range of devices from supercomputers to wristwatches. The Linux kernel is released under an open source license, so anyone can read and modify its code. It has been modified to run on a large variety of electronics. Although estimates suggest it is used on only 0.5-2% of all personal computers,[7] it has been widely adopted for use in servers and embedded systems[11][12] (such as cell phones). Linux has superseded Unix in most places[which?], and is used on the 10 most powerful supercomputers in the world[13]. Sony VAIO VGN-FZ190E/2 Battery<o:p>

The GNU project is a mass collaboration of programmers who seek to create a completely free and open operating system that was similar to Unix but with completely original code. It was started in 1983 by Richard Stallman, and is responsible for many of the parts of most Linux variants. For this reason, Linux is often called GNU/Linux. Thousands of pieces of software for virtually every operating system are licensed under the GNU General Public License. Meanwhile, the Linux kernel began as a side project of Linus Torvalds, a university student from Finland. In 1991, Torvalds began work on it, and posted information about his project on a newsgroup for computer students and programmers. He received a wave of support and volunteers who ended up creating a full-fledged kernel. Programmers from GNU took notice, and members of both projects worked to integrate the finished GNU parts into the linux kernel in order to create a full-fledged operating system. Sony VAIO VGN-FZ190E/B Battery<o:p>

Google Chrome OS<o:p>

An expected design of Google Chrome OS<o:p>

Main article: Google Chrome OS<o:p>

Chrome is an operating system based on the Linux kernel and designed by Google. Chrome targets computer users who spend most of their time on the Internet—it is technically only a web browser with no other applications, and relies on Internet applications used in the web browser to accomplish tasks such as word processing and media viewing.<o:p>

OtherSony VAIO VGN-FZ190N2 Battery<o:p>

Older operating systems which are still used in niche markets include OS/2 from IBM and Microsoft; Mac OS, the non-Unix precursor to Apple's Mac OS X; BeOS; XTS-300. Some, most notably Haiku, RISC OS, MorphOS, AmigaOS 4 and FreeMint continue to be developed as minority platforms for enthusiast communities and specialist applications. OpenVMS formerly from DEC, is still under active development by Hewlett-Packard. Yet other operating systems are used almost exclusively in academia, for operating systems education or to do research on operating system concepts. A typical example of a system that fulfills both roles is MINIX, while for example Singularity is used purely for research. Sony VAIO VGN-FZ190N3 Battery<o:p>

Components<o:p>

The components of an operating system all exist in order to make the different parts of a computer work together. All software—from financial databases to film editors—needs to go through the operating system in order to use any of the hardware, whether it be as simple as a mouse or keyboard or complex as an Internet connection.<o:p>

The user interface<o:p>

An example of the command line. Each command is typed out after the 'prompt', and then its output appears below, working its way down the screen. The current command prompt is at the bottom. Sony VAIO VGN-FZ190N4 Battery<o:p>

An example of a graphical user interface. Programs take the form of images on the screen, and the files, folders, and applications take the form of icons and symbols. A mouse is used to navigate the computer.<o:p>

Main article: User Interface<o:p>

Every computer that receives some sort of human input needs a user interface, which allows a person to interact with the computer. While devices like keyboards, mice and touchscreens make up the hardware end of this task, the user interface makes up the software for it. The two most common forms of a user interface have historically been the Command-line interface, where computer commands are typed out line-by-line, and the Graphical user interface, where a visual environment (most commonly with windows, buttons, and icons) is present. Sony VAIO VGN-FZ19VN Battery<o:p>

Graphical user interfaces<o:p>

Most of the modern computer systems support graphical user interfaces (GUI), and often include them. In some computer systems, such as the original implementations of Microsoft Windows and the Mac OS, the GUI is integrated into the kernel.<o:p>

While technically a graphical user interface is not an operating system service, incorporating support for one into the operating system kernel can allow the GUI to be more responsive by reducing the number of context switches required for the GUI to perform its output functions. Other operating systems are modular, separating the graphics subsystem from the kernel and the Operating System. In the 1980s UNIX, VMS and many others had operating systems that were built this way. GNU/Linux and Mac OS X are also built this way. Modern releases of Microsoft Windows such as Windows Vista implement a graphics subsystem that is mostly in user-space; however the graphics drawing routines of versions between Windows NT 4.0 and Windows Server 2003 exist mostly in kernel space. Windows 9x had very little distinction between the interface and the kernel. Sony VAIO VGN-FZ20 Battery<o:p>

Many computer operating systems allow the user to install or create any user interface they desire. The X Window System in conjunction with GNOME or KDE is a commonly found setup on most Unix and Unix-like (BSD, GNU/Linux, Solaris) systems. A number of Windows shell replacements have been released for Microsoft Windows, which offer alternatives to the included Windows shell, but the shell itself cannot be separated from Windows. Sony VAIO VGN-FZ21E Battery<o:p>

Numerous Unix-based GUIs have existed over time, most derived from X11. Competition among the various vendors of Unix (HP, IBM, Sun) led to much fragmentation, though an effort to standardize in the 1990s to COSE and CDE failed for various reasons, and were eventually eclipsed by the widespread adoption of GNOME and KDE. Prior to free software-based toolkits and desktop environments, Motif was the prevalent toolkit/desktop combination (and was the basis upon which CDE was developed).<o:p>

Graphical user interfaces evolve over time. For example, Windows has modified its user interface almost every time a new major version of Windows is released, and the Mac OS GUI changed dramatically with the introduction of Mac OS X in 1999.[14] Sony VAIO VGN-FZ21J Battery<o:p>

The kernel<o:p>

A kernel connects the application software to the hardware of a computer.<o:p>

Main article: Kernel (computing)<o:p>

With the aid of the firmware and device drivers, the operating system provides the most basic level of control over all of the computer's hardware devices. It manages memory access for programs in the RAM, it determines which programs get access to which hardware resources, it sets up or resets the CPU's operating states for optimal operation at all times, and it organizes the data for long-term non-volatile storage with file systems on such media as disks, tapes, flash memory, etc. Sony VAIO VGN-FZ21M Battery<o:p>

Program execution<o:p>

Main article: Process (computing)<o:p>

The operating system acts as an interface between an application and the hardware. The user interacts with the hardware from "the other side". The operating system is a set of services which simplifies development of applications. Executing a program involves the creation of a process by the operating system. The kernel creates a process by assigning memory and other resources, establishing a priority for the process (in multi-tasking systems), loading program code into memory, and executing the program. The program then interacts with the user and/or other devices and performs its intended function. Sony VAIO VGN-FZ21S Battery<o:p>

Interrupts<o:p>

Main article: interrupt<o:p>

Interrupts are central to operating systems, as they provide an efficient way for the operating system to interact with and react to its environment. The alternative—having the operating system "watch" the various sources of input for events (polling) that require action—can be found in older systems with very small stacks (50 or 60 bytes) but fairly, unusual in modern systems with fairly large stacks. Interrupt-based programming is directly supported by most modern CPUs. Interrupts provide a computer with a way of automatically saving local register contexts, and running specific code in response to events. Even very basic computers support hardware interrupts, and allow the programmer to specify code which may be run when that event takes place. Sony VAIO VGN-FZ21Z Battery<o:p>

When an interrupt is received, the computer's hardware automatically suspends whatever program is currently running, saves its status, and runs computer code previously associated with the interrupt; this is analogous to placing a bookmark in a book in response to a phone call. In modern operating systems, interrupts are handled by the operating system's kernel. Interrupts may come from either the computer's hardware or from the running program. Sony VAIO VGN-FZ25 Battery<o:p>

When a hardware device triggers an interrupt, the operating system's kernel decides how to deal with this event, generally by running some processing code. The amount of code being run depends on the priority of the interrupt (for example: a person usually responds to a smoke detector alarm before answering the phone). The processing of hardware interrupts is a task that is usually delegated to software called device driver, which may be either part of the operating system's kernel, part of another program, or both. Device drivers may then relay information to a running program by various means. Sony VAIO VGN-FZ250E/B Battery<o:p>

A program may also trigger an interrupt to the operating system. If a program wishes to access hardware for example, it may interrupt the operating system's kernel, which causes control to be passed back to the kernel. The kernel will then process the request. If a program wishes additional resources (or wishes to shed resources) such as memory, it will trigger an interrupt to get the kernel's attention.<o:p>

Modes<o:p>

Main articles: Protected mode and Supervisor mode<o:p>

Privilege rings for the x86 available in protected mode. Operating systems determine which processes run in each mode. Sony VAIO VGN-FZ27 Battery<o:p>

Modern CPUs support multiple modes of operation. CPUs with this capability use at least two modes: protected mode and supervisor mode. The supervisor mode is used by the operating system's kernel for low level tasks that need unrestricted access to hardware, such as controlling how memory is written and erased, and communication with devices like graphics cards. Protected mode, in contrast, is used for almost everything else. Applications operate within protected mode, and can only use hardware by communicating with the kernel, which controls everything in supervisor mode. CPUs might have other modes similar to protected mode as well, such as the virtual modes in order to emulate older processor types, such as 16-bit processors on a 32-bit one, or 32-bit processors on a 64-bit one. Sony VAIO VGN-FZ28 Battery<o:p>

When a computer first starts up, it is automatically running in supervisor mode. The first few programs to run on the computer, being the BIOS, bootloader and the operating system have unlimited access to hardware - and this is required because, by definition, initializing a protected environment can only be done outside of one. However, when the operating system passes control to another program, it can place the CPU into protected mode.<o:p>

In protected mode, programs may have access to a more limited set of the CPU's instructions. A user program may leave protected mode only by triggering an interrupt, causing control to be passed back to the kernel. In this way the operating system can maintain exclusive control over things like access to hardware and memory. Sony VAIO VGN-FZ280E/B Battery<o:p>

The term "protected mode resource" generally refers to one or more CPU registers, which contain information that the running program isn't allowed to alter. Attempts to alter these resources generally causes a switch to supervisor mode, where the operating system can deal with the illegal operation the program was attempting (for example, by killing the program).<o:p>

Memory management<o:p>

Main article: memory management<o:p>

Among other things, a multiprogramming operating system kernel must be responsible for managing all system memory which is currently in use by programs. This ensures that a program does not interfere with memory already used by another program. Since programs time share, each program must have independent access to memory. Sony VAIO VGN-FZ290 Battery<o:p>

Cooperative memory management, used by many early operating systems, assumes that all programs make voluntary use of the kernel's memory manager, and do not exceed their allocated memory. This system of memory management is almost never seen any more, since programs often contain bugs which can cause them to exceed their allocated memory. If a program fails, it may cause memory used by one or more other programs to be affected or overwritten. Malicious programs or viruses may purposefully alter another program's memory, or may affect the operation of the operating system itself. With cooperative memory management, it takes only one misbehaved program to crash the system. Sony VAIO VGN-FZ290EAB Battery<o:p>

Memory protection enables the kernel to limit a process' access to the computer's memory. Various methods of memory protection exist, including memory segmentation and paging. All methods require some level of hardware support (such as the 80286 MMU), which doesn't exist in all computers.<o:p>

In both segmentation and paging, certain protected mode registers specify to the CPU what memory address it should allow a running program to access. Attempts to access other addresses will trigger an interrupt which will cause the CPU to re-enter supervisor mode, placing the kernel in charge. This is called a segmentation violation or Seg-V for short, and since it is both difficult to assign a meaningful result to such an operation, and because it is usually a sign of a misbehaving program, the kernel will generally resort to terminating the offending program, and will report the error. Sony VAIO VGN-FZ29VN Battery<o:p>

Windows 3.1-Me had some level of memory protection, but programs could easily circumvent the need to use it. A general protection fault would be produced indicating a segmentation violation had occurred, however the system would often crash anyway.<o:p>

 

 MS-DOS

MS-DOS (pronounced / m s d s/, em-es-dos; short for MicroSoft Disk Operating System) is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system. Kingston HyperX-KHX1333C7D3K2/2G<o:p>

MS-DOS grew from a 1981 request by IBM for an operating system for its IBM PC range of personal computers. Microsoft quickly bought the rights to QDOS (Quick and Dirty Operating System), also known as 86-DOS,[1] from Seattle Computer Products, and began work on modifying it to meet IBM's specification. The first edition, MS-DOS 1.0, was launched in 1982.[2] The version shipped with IBM's PCs was called PC DOS. Although MS-DOS and PC-DOS were initially developed in parallel by Microsoft and IBM, the two products eventually went their separate ways. kingston- laptop -DDR3(1066)-1GB<o:p>

During its life, several competing products were released for the x86 platform,[3] and MS-DOS itself would go through eight versions, until development ceased in 2000. Ultimately it was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI.<o:p>

MS-DOS was a renamed form of 86-DOS — informally known as the Quick-and-Dirty Operating System or Q-DOS [2] — owned by Seattle Computer Products, written by Tim Paterson[2]. Microsoft needed an operating system for the then-new Intel 8086 but it had none available, so it licensed 86-DOS and released a version of it as MS-DOS 1.0[2]. kingston-Laptop-DDR3(1066)-2GB Development started in 1981, and MS-DOS 1.0 was released with the IBM PC in 1982[2]. (86-DOS, in turn, was written as an interim replacement for the delayed CP/M-86, when Seattle Computer Products' needed an operating system to sell with their 8086 processor card for the S-100 bus.) Tim Paterson is considered the original author of DOS and he is called "The Father of DOS"[2][n 1]. kingston-Laptop-DDR3(1333)-1GB)<o:p>

Worried by possible legal problems, in June 1981 Microsoft made an offer to Rod Brock, the owner of Seattle Computer, to buy the rights for 86-DOS. An agreement to release all rights to the software was signed in June 1981. The total cost was $75,000.[3][n 2]<o:p>

Originally MS-DOS was designed to be an operating system that could run on any 8086-family computer. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M, and with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS was designed with a modular structure with internal device drivers, minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, and installable device drivers for other devices loaded and integrated at boot time. kingston-Laptop-DDR3(1333)-2GBThe OEM would use a development kit provided by Microsoft to build a version of MS-DOS with their basic I/O drivers and a standard Microsoft kernel, which they would typically supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, and there is a major distinction between an IBM-compatible (or ISA) machine and an MS-DOS [compatible] machine. Some machines, like the Tandy 2000, were MS-DOS compatible but not IBM-compatible, so they could only run software written exclusively for MS-DOS without dependence on the peripheral hardware of the IBM PC architecture. kingston-D-DDR2(667)-1GB<o:p>

This design would have worked well for compatibility, if application programs had only used MS-DOS services to perform device I/O, and indeed the same design philosophy is embodied in Windows NT (see Hardware Abstraction Layer). However, in MS-DOS's early days, the greater speed attainable by programs through direct control of hardware was of particular importance, especially for games, which often pushed the limits of their contemporary hardware. Very soon an IBM-compatible architecture became the goal, and before long all 8086-family computers closely emulated IBM's hardware, and only a single version of MS-DOS for a fixed hardware platform was needed for the market. This version is the version of MS-DOS that is discussed here, as the dozens of other OEM versions of "MS-DOS" were only relevant to the systems they were designed for, and in any case were very similar in function and capability to the same-numbered standard version for the IBM PC, with a few notable exceptions. kingston-D-DDR2(667)-2GB<o:p>

While MS-DOS appeared on PC clones, true IBM computers used PC DOS, a rebranded form of MS-DOS. Ironically, the dependence on IBM-compatible hardware caused major problems for the computer industry when the original design had to be changed. For example, the original design could support no more than 640 kilobytes of memory (the 640 kB barrier), because IBM's hardware design reserved the address space above this limit for peripheral devices and ROM. Manufacturers had to develop complicated schemes (EMS and XMS, and other minor proprietary ones) to access additional memory. This limitation would not have been a problem if the original idea of interfacing with hardware through MS-DOS had endured. (However, MS-DOS was also a real-mode operating system, and the Intel x86 architecture only supports up to 1 MB of memory address space in Real Mode, even on Pentium 4 and later x86 CPUs, so for simple access to megabytes of memory, MS-DOS would have had to be rewritten to run in 80286 or 80386 Protected Mode.) kingston-D-DDR2(800)-2GB Also, Microsoft originally described MS-DOS as "an operating system for Intel 8086-based microcomputers", and the 8086 CPU (and its cousin the 8088) itself has only 1 MiB of total memory address space.<o:p>

[edit]Versions<o:p>

Main article: Comparison of x86 DOS operating systems<o:p>

Microsoft licensed or released versions of MS-DOS under different names like SB-DOS or Z-DOS[3]. Competitors released DOS systems such as DR-DOS and PTS-DOS that could also run DOS applications. The following versions of MS-DOS were released to the public:[4][5]<o:p>

Version 8.0 (WinME) - Integrated drivers for faster Windows loading. kingston-D-DDR2(800)-1GB<o:p>

Version 8.0 (WinXP) - DOS boot disks created by XP and later contain files from WinME. The internal DOS is still 5.0Microsoft DOS was released through the OEM channel, until DRI released DR-DOS 5.0 as a retail upgrade. With PC-DOS 5.00.1, the IBM-Microsoft agreement started to end, and IBM entered the retail DOS market with IBMDOS 5.00.1, 5.02, 6.00 and PC-DOS 6.10, 6.30, 7.00 and 2000.<o:p>

A number of beta versions have surfaced on the Internet, such as 5.0 (a ten-diskette version in the same vein as 4.0), 7.00 beta 1 (based on 6.00), 7.00 beta 2 (based on 6.22). An OEM source package for 6.00, and a late release of 6.2(b) have also been seen. These are not retail versions.<o:p>

[edit]Competitionkingston-D-DDR3(1066)-1GB<o:p>

This section needs additional citations for verification.<o:p>

Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2010)<o:p>

The original MS-DOS advertisement in 1981.<o:p>

On microcomputers based on the Intel 8086 and 8088 processors, including the IBM PC and clones, the initial competition to the PC DOS/MS-DOS line came from Digital Research, whose CP/M operating system had inspired MS-DOS. In fact, there remains controversy as to whether Q-DOS was more or less plagiarised from early versions of CP/M code. Digital Research released CP/M-86 a few months after MS-DOS, and it was offered as an alternative to MS-DOS and Microsoft's licensing requirements, but at a higher price. Executable programs for CP/M-86 and MS-DOS were not interchangeable with each other; much applications software was sold in both MS-DOS and CP/M-86 versions until MS-DOS became preponderant (later Digital Research operating systems could run both MS-DOS and CP/M-86 software). MS-DOS supported the simple .COM and the more advanced relocatable .EXE executable file formats; CP/M-86 a relocatable format using the file extension .CMD. kingston-D-DDR3(1066)-2GB<o:p>

Most of the machines in the early days of MS-DOS had differing system architectures and there was a certain degree of incompatibility, and subsequently vendor lock-in. Users who began using MS-DOS with their machines were compelled to continue using the version customized for their hardware, or face trying to get all of their proprietary hardware and software to work with the new system.<o:p>

In the business world the 808x-based machines that MS-DOS was tied to faced competition from the Unix operating system which ran on many different hardware architectures. Microsoft itself sold a version of Unix for the PC called Xenix. kingston-D-DDR3(1333)-1GB<o:p>

In the emerging world of home users, a variety of other computers based on various other processors were in serious competition with the IBM PC: the Apple II, early Apple Macintosh, the Commodore 64 and others did not use the 808x processor; many 808x machines of different architectures used custom versions of MS-DOS. At first all these machines were in competition. In time the IBM PC hardware configuration became dominant in the 808x market as software written to communicate directly with the PC hardware without using standard operating system calls ran much faster, but on true PC-compatibles only. Non-PC-compatible 808x machines were too small a market to have fast software written for them alone, and the market remained open only for IBM PCs and machines that closely imitated their architecture, all running either a single version of MS-DOS compatible only with PCs, or the equivalent IBM PC DOS. Most clones cost much less than IBM-branded machines of similar performance, and became widely used by home users, while IBM PCs had a large share of the business computer market. kingston-D-DDR3(1333)-2GB<o:p>

Microsoft and IBM together began what was intended as the follow-on to MS/PC DOS, called OS/2. When OS/2 was released in 1987, Microsoft began an advertising campaign announcing that "DOS is Dead" and stating that version 4 was the last full release. OS/2 was designed for efficient multi-tasking — an IBM speciality derived from deep experience with mainframe operating systems — and offered a number of advanced features that had been designed together with similar look and feel; it was seen as the legitimate heir to the "kludgy" DOS platform. KHX6400D2LLK/2G<o:p>

MS-DOS had grown in spurts, with many significant features being taken or duplicated from Microsoft's other products and operating systems. MS-DOS also grew by incorporating, by direct licensing or feature duplicating, the functionality of tools and utilities developed by independent companies, such as Norton Utilities, PC Tools (Microsoft Anti-Virus), QEMM expanded memory manager, Stacker disk compression, and others. KHX1333C7D3K2/2GB(2-1GB)<o:p>

During the period when Digital Research was competing in the operating system market some computers, like Amstrad PC-1512, were sold with floppy disks for two operating systems (only one of which could be used at a time), MS-DOS and CP/M-86 or a derivative of it. Digital Research produced DOS Plus, which was compatible with MS-DOS 2.11, supported CP/M-86 programs, had additional features including multi-tasking, and could read and write disks in CP/M and MS-DOS format. KHX1333C7D3K2/4GB(2-2GB)<o:p>

While OS/2 was under protracted development, Digital Research released the MS-DOS compatible DR-DOS 5, which included features only available as third-party add-ons for MS-DOS (and still maintained considerable internal CP/M-86 compatibility). Unwilling to lose any portion of the market, Microsoft responded by announcing the "pending" release of MS-DOS 5.0 in May 1990. This effectively killed most DR-DOS sales until the actual release of MS-DOS 5.0 in June 1991. Digital Research brought out DR-DOS 6, which sold well until the "pre-announcement" of MS-DOS 6.0 again stifled the sales of DR-DOS. KHX1600C9D3BK2/4G(2-2GB)<o:p>

Microsoft had been accused of carefully orchestrating leaks about future versions of MS-DOS in an attempt to create what in the industry is called FUD (fear, uncertainty, and doubt) regarding DR-DOS. For example, in October 1990, shortly after the release of DR-DOS 5.0, and long before the eventual June 1991 release of MS-DOS 5.0, stories on feature enhancements in MS-DOS started to appear in InfoWorld and PC Week. Brad Silverberg, Vice President of Systems Software at Microsoft and General Manager of its Windows and MS-DOS Business Unit, wrote a forceful letter to PC Week (November 5, 1990), denying that Microsoft was engaged in FUD tactics ("to serve our customers better, we decided to be more forthcoming about version 5.0") and denying that Microsoft copied features from DR-DOS: KHX1600C9D3K2/4G(2-2GB)<o:p>

"The feature enhancements of MS-DOS version 5.0 were decided and development was begun long before we heard about DR-DOS 5.0. There will be some similar features. With 50 million MS-DOS users, it shouldn't be surprising that DRI has heard some of the same requests from customers that we have." – (Schulman et al. 1994). [6]<o:p>

The pact between Microsoft and IBM to promote OS/2 began to fall apart in 1990 when Windows 3.0 became a marketplace success. Much of Microsoft's further contributions to OS/2 also went in to creating a third GUI replacement for DOS, Windows NT. KHX1800C9D3K2/4GX(2-2GB)<o:p>

IBM, which had already been developing the next version of OS/2, carried on development of the platform without Microsoft and sold it as the alternative to DOS and Windows.<o:p>

[edit]Legal issues<o:p>

As a response to Digital Research's DR-DOS 6.0, which bundled SuperStor disk compression, Microsoft opened negotiations with Stac Electronics, vendor of the most popular DOS disk compression tool, Stacker. In the due diligence process, Stac engineers had shown Microsoft part of the Stacker source code. Stac was unwilling to meet Microsoft's terms for licensing Stacker and withdrew from the negotiations. Microsoft chose to license Vertisoft's DoubleDisk, using it as the core for its DoubleSpace disk compression[7]. KHX1800C9D3K2/2GX(2-1GB)<o:p>

MS-DOS 6.0 and 6.20 were released in 1993, both including the Microsoft DoubleSpace disk compression utility program. Stac successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. This resulted in the 1994 release of MS-DOS 6.21, which had disk-compression removed. Shortly afterwards came version 6.22, with a new version of the disk compression system, DriveSpace, which had a different compression algorithm to avoid the infringing code. KHX1333C7D3K2/4GX(2-2GB)<o:p>

Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR-DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft's licensing procedures, resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera, sued Microsoft for damages. This lawsuit was settled with a monetary payment of $150 million. ing ddr 3 King ddr 3 KHX1333C7D3K2/2GX(2-1GB)<o:p>

[edit]Use of undocumented APIs<o:p>

Microsoft also used a variety of tactics in MS-DOS and several of their applications and development tools that, while operating perfectly when running on genuine MS-DOS (and PC DOS), would break when run on another vendor's implementation of DOS. Notable examples of this practice included:<o:p>

Microsoft's QuickPascal released in early 1989 was the first MS product that checked for MS-DOS by modifying the program's Program Segment Prefix using undocumented DOS functions, and then checked whether or not the associated value changed in a fixed position within the DOS data segment (also undocumented). This check also made it into later MS products, including Microsoft QuickC v2.5, Programmer's Workbench and Microsoft C v6.0[6]. KINGSTON DDR3 KHX1600C7D3K2/4GX(2-2GB)<o:p>

The (once infamous) AARD code, a block of code in the Windows 3.1 beta installer. It was XOR encrypted, self-modifying, and deliberately obfuscated, using various undocumented DOS structures and functions to determine whether or not Windows really was running on MS-DOS[6].<o:p>

Note that the Windows 3.0 beta code only gave a warning that Windows would not operate properly on a "foreign" OS. It did in fact run just fine on DR-DOS 6.0.<o:p>

Interrupt routines called by Windows to inform MS-DOS that Windows is starting/exiting, information that MS-DOS retained in an IN_WINDOWS flag, in spite of the fact that MS-DOS and Windows were supposed to be two separate products[6].<o:p>

[edit]End of MS-DOSWd Elements portable 500GB<o:p>

MS-DOS lingers in Windows 7.<o:p>

Today, MS-DOS is rarely used for desktop computing. Since the release of Windows 95, it was integrated as a full product used for bootstrapping and troubleshooting, and no longer released as a standalone product.<o:p>

Windows XP contains a copy of the core MS-DOS 8 files from Windows Me, accessible only by formatting a floppy as an "MS-DOS startup disk". These core files are a stripped down bootstrap only, which does not include CD-ROM support. With Windows Vista the files on the startup disk are dated 18 April 2005 but are otherwise unchanged, including the string "MS-DOS Version 8 (C) Copyright 1981-1999 Microsoft Corp" inside COMMAND.COM. Wd Elements SE portable 750GB<o:p>

However the only versions of DOS currently recognized as stand-alone OSs, and supported as such by the Microsoft Corporation are DOS 6.0 and 6.22, both of which remain available for download via their MSDN, volume license, and OEM license partner websites, for customers with valid login credentials.<o:p>

Today, DOS is still used in embedded x86 systems due to its simple architecture, and minimal memory and processor requirements. The command line interpreter of NT-based versions of Windows, cmd.exe, maintains most of the same commands and some compatibility with DOS batch files. wd passport essential 500gb<o:p>

Microsoft has introduced a new command-line called PowerShell. Powershell offers more functionality than MS-DOS.<o:p>

[edit]The Windows command-line interface<o:p>

All versions of Microsoft Windows have had an MS-DOS like command-line interface (CLI). This could run many DOS and variously Win32, OS/2 1.x and Posix command line utilities in the same command-line session, allowing piping between commands. The user interface, and the icon up to Windows 2000, followed the native MS-DOS interface. wd passport essential 250GB blue<o:p>

Consumer Windows (up to 3.11, Win9x, WinME) ran as a Graphical User Interface (GUI) running on top of MS-DOS. With Windows 95, 98, and ME the MS-DOS part was integrated to give the illusion of a new operating system. The command line accessed the DOS command line (usually command.com), through a Windows module (winoldap.mod).<o:p>

A new line of Windows, (Windows NT), boot through a kernel whose sole purpose is to load Windows: there is no character-mode boot similar to Consumer Windows, OS/2 or UNIX). The console runs as a Win32 session, with the default processor cmd.exe being a feature-reduced version of OS/2's version. The command session permits running of various supported command line utilities from Win32, MS-DOS, OS/2 1.x and POSIX. wd passport essential 500GB blue<o:p>

<o:p> 

The 32-bit Windows can run MS-DOS programs through the use of the NTVDM (NT Virtual DOS Machine). This launches a hacked version of MS-DOS 5.0. Launching the DOS command processor command.com creates a DOS environment that allows DOS programs to communicate with each other. It is not usually run by Windows, and the internal commands of command.com are processed by the underlying Win32 processor (usually cmd.exe, but could be 4nt).<o:p>

The 32-bit CLI is usually referred to as the MS-DOS prompt. Although the binary interface is no longer that found in PC-DOS etc., it is an 'interface', and not an API. The commands typed here, the batches etc., all resemble those of MS/PC-DOS in much the same way that the Linux/UNIX commands resemble each other without underlying binary compatibility. wd passport essential 250GB silver<o:p>

All versions of Windows for x86-64 and Itanium architectures no longer include the NTVDM and can therefore no longer natively run MS-DOS or 16-bit Windows applications. There are alternatives in the form of Virtual machine emulators such as Microsoft's own Virtual PC, as well as VMware, DOSBox, and others.<o:p>

[edit]Legacy compatibility<o:p>

From 1983 onwards, various companies worked on graphical user interfaces (GUIs) capable of running on PC hardware. With DOS being the dominant operating system several companies released alternate shells, e.g. Microsoft Word for DOS, XTree, and the Norton Shell. However, this required duplication of effort and did not provide much consistency in interface design (even between products from the same company). wd passport essential 320GB silver<o:p>

Later, in 1985, Microsoft Windows was released as Microsoft's first attempt at providing a consistent user interface (for applications). The early versions of Windows ran on top of MS-DOS and its clones. At first Windows met with little success, but this was also true for most other companies' efforts as well, for example GEM. After version 3.0 (1990), Windows gained market acceptance.<o:p>

Later versions (Windows 95, Windows 98 and Windows Me) used the DOS boot process to launch itself into protected mode. Basic features related to the file system, such as long file names, were only available to DOS when running as a subsystem of Windows. Windows NT ran independently of DOS but included a DOS subsystem so applications could run in a virtual machine under the new OS. With the latest Windows releases, even dual-booting MS-DOS is problematic as DOS may not be able to read the basic file system. wd passport essential 500GB silver<o:p>

DR-DOS<o:p>

DR-DOS (originally DR DOS up to including 6.0) is a DOS-type operating system for IBM PC-compatible personal computers, originally developed by Gary Kildall's Digital Research and derived from Digital Research's Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86.<o:p>

Digital Research's original CP/M for the 8-bit Intel 8080 and Z-80 based systems spawned numerous spin-off versions, most notably CP/M-86 for the Intel 8086/8088 family of processors. Although CP/M had dominated the market, and was shipped with the vast majority of non-proprietary-architecture personal computers, the IBM PC in 1981 brought the beginning of what was eventually to be a massive change. wd passport essential 250GB red<o:p>

IBM originally approached Digital Research, seeking an x86 version of CP/M. However, there were disagreements over the contract, and IBM withdrew. Instead, a deal was struck with Microsoft, who purchased another operating system, 86-DOS, from Seattle Computer Products. This became Microsoft MS-DOS and IBM PC DOS. 86-DOS' command structure and application programming interface imitated that of CP/M. Digital Research threatened legal action, claiming PC/MS-DOS to be too similar to CP/M. IBM settled by agreeing to sell their x86 version of CP/M, CP/M-86, alongside PC DOS. However, PC DOS sold for $60, while CP/M-86 had a $240 price tag. The proportion of PC buyers prepared to spend four times as much to buy CP/M-86 was very small, and the availability of compatible application software, at first decisively in Digital Research's favor, was only temporary.[1] wd passport essential 320GB red<o:p>

Digital Research fought a long losing battle to promote CP/M-86, and eventually decided that they could not beat the Microsoft-IBM lead in application software availability, so they modified CP/M-86 to allow it to run the same applications as MS-DOS and PC DOS. Initially, they sold DOS Plus, which ran applications for both platforms. It did not perform well, and Digital Research made another attempt, this time a fully DOS system. The new disk operating system was launched in 1988 as DR DOS.<o:p>

Although DRI was based in Monterey, California, USA, all of the operating system work on Concurrent DOS, Multiuser DOS, DOS Plus, DR DOS and PalmDOS was done in DRI's European Development Center (EDC) in Hungerford, UK. wd passport essential 500GB red<o:p>

[edit]First DR DOS version<o:p>

The first DR DOS version was released in May 1988. Version numbers were chosen to reflect features relative to MS-DOS; the first version promoted to the public was DR DOS 3.31, which offered features comparable to Compaq MS-DOS 3.31 with large disk support (FAT16B aka "BIGDOS"). DR DOS 3.31 reported itself as "PC DOS 3.31", while the internal BDOS (Basic Disk Operating System) kernel version was reported as 6.0, single-user nature, reflecting its origin as derivative of Concurrent DOS 6.0 with the multitasking and multiuser capabilities as well as CP/M API support stripped out and the XIOS replaced by an IBM-compatible DOS-BIOS. The system files were named DRBIOS.SYS (for the DOS-BIOS) and DRBDOS.SYS (for the BDOS kernel), the disk OEM label used was "DIGITAL".wd passport essential 320GB white<o:p>

Although DR DOS offered some extended command line tools with command line help, verbose error messages, sophisticated command line history and editing (HISTORY directive) as well as support for file and directory passwords built right into the kernel, DR DOS was cheaper to license than MS-DOS. Also, DR DOS was ROMable right from the start. As a result, DRI was approached by a number of PC manufacturers who were interested in a third-party DOS, and this prompted several updates to the system. wd passport essential 500GB white<o:p>

At this time, MS-DOS was only available to OEMs bundled with hardware. Consequently, DR DOS achieved some immediate success when it became possible for consumers to buy it through normal retail channels since 3.4x.<o:p>

Known versions are DR DOS 3.31 (BDOS 6.0, 1988-06, OEM only), 3.32 (BDOS 6.0, 1988-08-17, OEM only), 3.33 (BDOS 6.0, 1988-09-01, OEM only), 3.34 (OEM only), 3.35 (BDOS 6.0, 1988-10-21, OEM only), 3.40, 3.41 (BDOS 6.3, 1989-06, OEM and retail), most of them existed in several flavors for different OEMs. While most OEMs just kept the DR DOS name designation, one OEM version is known to be called EZ-DOS 3.41. wd passport essential 500GB black<o:p>

Further information: Comparison of x86 DOS operating systems<o:p>

[edit]Version 5.0<o:p>

This section does not cite any references or sources.<o:p>

Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2008)<o:p>

DR DOS version 5.0 (code-named "Leopard") was released in May 1990, still reporting itself as "PC DOS 3.31" for compatibility purposes, but internally indicating a single-user BDOS 6.4 kernel. (Version 4 was skipped to avoid being associated with the relatively unpopular MS-DOS 4.0.) This introduced ViewMAX, a GEM based GUI file management shell, and bundled disk-caching software, and also offers vastly improved memory management. For compatibility purposes, the DR DOS 5.0 system files were now named IBMBIO.COM (for the DOS-BIOS) and IBMDOS.COM (for the BDOS kernel), and the OEM label in boot sectors was changed to "IBM  3.3".wd passport essential 500GB red<o:p>

<o:p> 

First, the DR DOS kernel and structures such as disk buffers can be located in the High Memory Area (HMA), the first 64KB of extended memory which are accessible in real mode due to an incomplete compatibility of the 80286 with earlier processors. This freed up the equivalent amount of critical "base" or conventional memory, the first 640KB of the PC's RAM – the area in which all MS-DOS applications run.<o:p>

Additionally, on Intel 80386 machines, DR DOS's EMS memory manager allowed the OS to load DOS device drivers into upper memory blocks, further freeing base memory. For more information on this, see the article on the Upper Memory Area (UMA). wd passport essential 500GB red<o:p>

DR DOS 5.0 was the first DOS to integrate such functionality into the base OS (loading device drivers into upper memory blocks was possible using QEMM and MS-DOS). As such, on a 386 system, it could offer vastly more free conventional memory than any other DOS. Once drivers for a mouse, multimedia hardware and a network stack were loaded, an MS-DOS machine typically might only have 300 to 400KB of free conventional memory – too little to run most late-1980s software. DR DOS 5.0, with a small amount of manual tweaking, could load all this and still keep all of its conventional memory free – allowing for some necessary DOS data structures, as much as 620KB out of the 640KB. wd Passport Essential SE portable 1TB<o:p>

Because DR DOS leaves so much conventional memory available, some programs fail to load as they start "impossibly" low in memory – inside the first 64KB (known as "low memory"). DR DOS 5.0's new MEMMAX -L command works around this by leaving a small empty space at the start of the memory map.<o:p>

[edit]Competition from Microsoft<o:p>

Faced with substantial competition in the DOS arena, Microsoft responded with an announcement of a yet-to-be released MS-DOS 5.0 in May 1990. This would be released in 1991 and include similar advanced features to those of DR DOS. It included matches of the DR's enhancements in memory management. wd Passport Essential SE 1TB USB 3.0<o:p>

Almost immediately in May 1991, DR responded with DR DOS 6.0, code-named "Buxton". DR DOS 6.0, while already at BDOS level 6.7 internally, would still report itself as "PC DOS 3.31" to normal DOS applications for compatibility purposes. This bundled in SuperStor on-the-fly disk compression, to maximize available hard disk space, and file deletion tracking and undelete functionality.<o:p>

DR DOS 6.0 also includes a task-switcher named TASKMAX, supporting the industry standard task-switching API to run multiple applications at the same time. In contrast to Digital Research's Multiuser DOS (successor of Concurrent DOS in the multi-user products line), which would run DOS applications in pre-emptively multitasked virtual DOS machines, the DR DOS 6.0 task switcher would freeze background applications until brought back into the foreground. While it runs on x86-machines, it is able to swap to XMS memory on 286+ machines. TASKMAX did support some Copy & Paste facility between applications. Via the task-switcher API graphical user interfaces such as ViewMax or PC/GEOS could register as task manager menu and thereby replace the TASKMAX text mode menu, so that users could switch between tasks from within a GUI. wd Passport Essential SE 1TB USB 3.0 RED<o:p>

Microsoft responded with MS-DOS 6.0, which again matched some features of DR DOS 6.0.<o:p>

A pre-release version of Windows 3.1 was designed to return a non-fatal error message if it detected a non-Microsoft DOS. This check came to be known as the AARD code[2]. With the detection code disabled, Windows ran perfectly under DR DOS and its successor Novell DOS. The code was present but disabled in the released version of Windows 3.1[3] wd Passport Essential SE 1TB USB 3.0 blue<o:p>

[edit]Patching to counter Microsoft<o:p>

It was a simple matter for Digital Research to patch DR DOS 6.0 to circumvent the AARD 'authenticity check' in Windows 3.1 beta by rearranging the order to two internal tables in memory (with no changes in functionality), and the patched version was on the streets within six weeks of the release of Windows 3.1. With improved marketing and packaging, very advanced memory management, disk compression and the Super PC-Kwik caching software, DR DOS 6.0 was an outstanding value and easily the most successful version.[citation needed] wd Passport Essential SE 1TB USB 3.0 sliver<o:p>

[edit]PalmDOS<o:p>

In 1992 Digital Research also embarked on a spin-off product code-named "Merlin" and later released as NetWare PalmDOS 1, which, as its name implies, was a very resource light DR DOS 6.0 derivative aimed at the emerging Palmtop/PDA market.<o:p>

PalmDOS was the first operating system in the family to sport the new BDOS 7.0 kernel with native DOS compatible internal data structures instead of emulations thereof. Replacing the DOS emulation on top of a CP/M kernel by a true DOS compatible kernel helped a lot in improving compatibility with some applications using some of DOS' internal data structures and also was the key in reducing the resident size of the kernel code even further - a particular requirement for the PDA market. On the other hand, introducing a genuine Current Directory Structure (CDS) imposed a limit on the depth of working directories down to 66 characters (as in MS-DOS/PC DOS), whereas previous issues of DR DOS had no such limitation due to their internal organization of directories as relative links to parent directories instead of as absolute paths. Seagate freeagent Go 250GB black<o:p>

As well as a ROM-executing kernel, PalmDOS had palmtop-type support for features such as PCMCIA PC Cards, Power Management (BatteryMAX and the IDLE$ device driver with its patented dynamic idle detection by Roger Gross and John Constant), MINIMAX task switcher support for PIM (Personal Information Modules) applications stored and executed from ROM via XIP (Execute In-Place), etc.<o:p>

The PCMCIA stack for PalmDOS was partially written by Ian Cullimore. Seagate freeagent Go 320gb black<o:p>

[edit]Contribution by Novell<o:p>

Networking giant Novell bought Digital Research with a view to using DR's product line as a lever in their comprehensive strategy to break the Microsoft monopoly. (This was part of a massive and ultimately disastrous spending spree for Novell: they bought WordPerfect Corporation at about the same time, some of Borland's products, and invested heavily in Unix as well.) The planned DR DOS 7.0, internally named "Panther", intended to trump Microsoft's troubled MS-DOS 6.0, was repeatedly delayed, while Novell was working on an Unix-like multi-user security extension (compatible with its Multiuser DOS) and two new graphical user interfaces (ViewMAX/3, a derivative of GEM, and "Star Trek", a true port of Apple's MacOS 7.1 to run under the new DR DOS multitasker named "Vladivar").Seagate freeagent Go 640GB black<o:p>

When DR DOS eventually arrived, renamed Novell DOS 7, and without these three components, it was a disappointment to some. It was larger and introduced many new bugs, and the main functional addition was Novell's second attempt at a peer-to-peer networking system, Personal NetWare (PNW). This worked and was better than its predecessor, NetWare Lite, but it was incompatible with Microsoft's networking system, now growing popular with support in Windows for Workgroups, OS/2 and Windows NT. A considerable amount of manual configuration was needed to get both to co-exist on the same PC, and Personal NetWare never achieved much success. Seagate freeagent Go 500GB Blue<o:p>

Novell DOS 7 introduced much advanced memory management including new support for DPMI (DOS Protected Mode Interface) and DPMS (DOS Protected Mode Services) as well as more flexible loadhigh options. It also introduced support for "true" pre-emptive multitasking of multiple DOS applications in virtual DOS machines (VDM), similar to Multiuser DOS, but now on the basis of a natively DOS compatible environment, similar to Windows 386 Enhanced Mode without GUI. By default, the bundled TASKMGR would behave similar to the former DR DOS 6.0 TASKMAX. However, if EMM386 was loaded with the option /MULTI, EMM386 would load a natively 32-bit 386 Protected Mode operating system core providing API support for pre-emptive multitasking, multi-threading, hardware virtualization and domain management of virtual DOS machines. This API could be used by DR DOS-aware applications. If TASKMGR was run later on, it would use these APIs to instance the current 16-bit DOS system environment, create virtual DOS machines and run applications in them instead of using its own Real Mode task-switcher support. The multitasker was compatible with Windows, so that tasks started before launching Windows could be seen as tasks under Windows as well. Seagate freeagent Goflex 500GB<o:p>

[edit]After Novell<o:p>

Novell DOS 7 required several bug-fix releases and was not completely stable when the next development occurred. Realising eventually that their formidable networking skills did not translate into other areas, Novell wound down further development on Novell DOS 7 in 1994 and stopped maintenance at the end of 1995 after more than 15 updates. When Caldera approached Novell looking for a DOS operating system to bundle with their OpenLinux distribution, Novell sold the product line off to Caldera in 1996, by which time it was of little commercial value. Seagate freeagent Goflex pro 500GB<o:p>

Between the now-Caldera owned DR-DOS and competition from IBM's PC DOS 6.3, Microsoft moved to make it impossible to use or buy the subsequent Windows version, Windows 95, with any DOS product other than their own. Claimed by them to be a purely technical change, this was later to be the subject of a major lawsuit brought in Salt Lake City by Caldera.[4] Microsoft lawyers tried repeatedly to have the case thrown out but without success. Immediately after the completion of the pre-trial deposition stage (where the parties list the evidence they intend to present), there was an out-of-court settlement for an undisclosed sum.[5] This was revealed in November 2009 to be $280 million dollars. Seagate freeagent Goflex 500GB blue <o:p>

In 1997, the US-based Caldera, Inc. opened a new subsidiary Caldera UK Ltd. in Andover, UK, nearby the former Digital Research and Novell EDC. Caldera UK hired some of the original developers of the operating system as well as some new talents to continue work on the operating system and besides other features subsequently add a TCP/IP stack, a graphical HTML 3.2 web-browser DR-WebSpyder with LAN and modem dialup, a Posix pthreads extension, long filename (LONGNAME) as well as LBA and FAT32 support (DRFAT32). They also worked on DR-DOS "WinGlue"/"WinBolt", versions of DR-DOS compatible with Windows 95, 98 and 98 SE, which remain unreleased up to the present, but played an important role in the court case. Seagate freeagent Goflex 500GB silver <o:p>

Caldera UK released parts of the operating system as open source, under the name "Caldera OpenDOS". OpenDOS was released as version 7.01 and 7.02, and the source was then closed again. (Version 7.02 was called "Caldera OpenDOS 7.02" while in beta testing; by the time it was released in December 1997, it was branded "Caldera DR-OpenDOS 7.02". The next release came in March 1998; it was branded "Caldera DR-DOS 7.02") Another version was released, 7.03, before Caldera US closed the successful UK operation at the beginning of 1999 in the attempt to cut costs and move the development into the US (which never worked out due to total lack of expertise in this field at Caldera, Inc.) and transferred the DR-DOS line to a branch company, Caldera Thin Clients, which would later become Lineo. Lineo would later re-release 7.03, still branded as "Caldera DR-DOS"[6] The licence terms of this release were incompatible witSamsung G2 portable 500GB<o:p>

h most if not all existing open source licences. Later releases of DR-DOS remain closed source.<o:p>

The last Lineo version was OEM DR-DOS 7.04/7.05, still branded as "Caldera DR-DOS".[7][8] This was an embedded system consisting only of the kernel and command shell. It was built for Seagate Technology's Seatools, with a buggy implementation of FAT32 and large hard disk support.[9]<o:p>

[edit]Recent versions<o:p>

In 2002, Lineo was bought out, and some of Lineo's former managers purchased the name and formed a new company, DeviceLogics. They have continued to sell DR-DOS for use in embedded systems. DR-DOS 8.0 was released on 30 March 2004 featuring FAT32 and large disk support, the ability to boot from ROM or Flash, multitasking and a DPMI memory manager. This version was based on the kernel from version 7.03.[10] The company then split into Devicelogics Inc. and DRDOS Inc, which released DR-DOS 8.1 (with better FAT32 support) in autumn 2005. This version was not based upon version 8.0, but was a complete rewrite. Both 8.0 and 8.1 have now been pulled (because of the discoveries outlined below), and replaced with Caldera DR-DOS 7.03.<o:p>

Aside from selling copies of the operating system, the DR DOS Inc. website lists a buyout option for DR-DOS; the asking price is $25,000.[11] Samsung G2 portable green 320GB<o:p>

The OpenDOS 7.01 source code is still actively being developed by The DR-DOS/OpenDOS Enhancement Project, founded in July 2002 in an attempt to bring the functionality of DR-DOS up to parity with modern PC operating systems. The project's efforts have resulted so far in adding native support for large disks (LBA) and the FAT32 filesystem. There were also several other enhancements, including improved memory management and support for the new FAT+ filesystem extension which allows files of almost 256 GB in size on normal FAT partitions. The project remains in active development as of August 2009. Samsung G2 portable green 640GB<o:p>

[edit]Controversies<o:p>

In October 2005, it was discovered that DR-DOS 8.1 included several utilities from FreeDOS and other sources and that the kernel was an outdated version of the Enhanced DR-DOS kernel. DR DOS Inc. failed to comply with the GNU General Public License (GPL) by not crediting the FreeDOS utilities to their authors and including the source code.[10] After complaints from FreeDOS developers (including the suggestion to provide the source code, and hence comply with the GPL), DR DOS Inc. instead pulled all 8.x versions (including the unaffected DR-DOS 8.0) from their website.<o:p>

 

BIOS and booting

From Wikipedia, the free encyclopedia<o:p>

In IBM PC Compatible computers, the basic input/output system (BIOS), also known as the System BIOS, is a de facto standard defining a firmware interface.[1]<o:p>

Phoenix AwardBIOS CMOS (non-volatile memory) Setup utility on a standard PC<o:p>

The BIOS software is built into the PC, and is the first code run by a PC when powered on ('boot firmware'). The primary function of the BIOS is to load and start an operating system. When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk, CD/DVD drive and other hardware. The BIOS then locates software held on a peripheral device (designated as a 'boot device'), such as a hard disk or a CD, and loads and executes that software, giving it control of the PC.[2] This process is known as booting, or booting up, which is short for bootstrapping. Sony VAIO VGN-FZ11E Battery<o:p>

BIOS software is stored on a non-volatile ROM chip built into the system on the mother board. The BIOS software is specifically designed to work with the particular type of system in question, including having a knowledge of the workings of various devices that make up the complementary chipset of the system. In modern computer systems, the BIOS chip's contents can be rewritten allowing BIOS software to be upgraded. Sony VAIO VGN-FZ11L Battery<o:p>

A BIOS will also have a user interface (or UI for short). Typically this is a menu system accessed by pressing a certain key on the keyboard when the PC starts. In the BIOS UI, a user can:<o:p>

configure hardware<o:p>

set the system clock<o:p>

enable or disable system components<o:p>

select which devices are eligible to be a potential boot device<o:p>

set various password prompts, such as a password for securing access to the BIOS UI functions itself and preventing malicious users from booting the system from unauthorized peripheral devices. Sony VAIO VGN-FZ11M Battery<o:p>

The BIOS provides a small library of basic input/output functions used to operate and control the peripherals such as the keyboard, text display functions and so forth, and these software library functions are callable by external software. In the IBM PC and AT, certain peripheral cards such as hard-drive controllers and video display adapters carried their own BIOS extension ROM, which provided additional functionality. Operating systems and executive software, designed to supersede this basic firmware functionality, will provide replacement software interfaces to applications. Sony VAIO VGN-FZ11S Battery<o:p>

The role of the BIOS has changed over time; today BIOS is a legacy system, superseded by the more complex Extensible Firmware Interface (EFI), but BIOS remains in widespread use, and EFI booting has only been supported in x86 Windows since 2008. BIOS is primarily associated with the 16-bit and 32-bit architecture eras (x86-32), while EFI is used for some 32-bit and most 64-bit architectures. Today BIOS is primarily used for booting a system, and for certain additional features such as power management (ACPI) and video initialization (in X.org), but otherwise is not used during the ordinary running of a system, while in early systems (particularly in the 16-bit era), BIOS was used for hardware access – operating systems (notably MS-DOS) would call the BIOS rather than directly accessing the hardware. In the 32-bit era and later, operating systems instead generally directly accessed the hardware using their own device drivers. However, the distinction between BIOS and EFI is rarely made in terminology by the average computer user, making BIOS a catch-all term for both systems. Sony VAIO VGN-FZ11Z Battery<o:p>

The term first appeared in the CP/M operating system, describing the part of CP/M loaded during boot time that interfaced directly with the hardware (CP/M machines usually had only a simple boot loader in their ROM). Most versions of DOS have a file called "IBMBIO.COM" or "IO.SYS" that is analogous to the CP/M BIOS.<o:p>

Among other classes of computers, the generic terms boot monitor, boot loader or boot ROM were commonly used. Some Sun and PowerPC-based computers use Open Firmware for this purpose. There are a few alternatives for Legacy BIOS in the x86 world: Extensible Firmware Interface, Open Firmware (used on the OLPC XO-1) and coreboot. Sony VAIO VGN-FZ130E/B Battery<o:p>

IBM PC-compatible BIOS chips<o:p>

In principle, the BIOS in ROM was customized to the particular manufacturer's hardware, allowing low-level services (such as reading a keystroke or writing a sector of data to diskette) to be provided in a standardized way to the operating system. For example, an IBM PC might have had either a monochrome or a color display adapter, using different display memory addresses and hardware - but the BIOS service to print a character on the screen in text mode would be the same. Sony VAIO VGN-FZ140E Battery<o:p>

Boot Block<o:p>

DMI Block<o:p>

Main Block<o:p>

PhoenixBIOS D686. This BIOS chip is housed in a PLCC package, which is, in turn, plugged into a PLCC socket.<o:p>

Prior to the early 1990s, BIOSes were stored in ROM or PROM chips, which could not be altered by users. As its complexity and need for updates grew, and re-programmable parts became more available, BIOS firmware was most commonly stored on EEPROM or flash memory devices. According to Robert Braver, the president of the BIOS manufacturer Micro Firmware, Flash BIOS chips became common around 1995 because the electrically erasable PROM (EEPROM) chips are cheaper and easier to program than standard erasable PROM (EPROM) chips. EPROM chips may be erased by prolonged exposure to ultraviolet light, which accessed the chip via the window. Chip manufacturers use EPROM programmers (blasters) to program EPROM chips. Electrically erasable (EEPROM) chips come with the additional feature of allowing a BIOS reprogramming via higher-than-normal amounts of voltage.[3] BIOS versions are upgraded to take advantage of newer versions of hardware and to correct bugs in previous revisions of BIOSes.[4] Sony VAIO VGN-FZ140QE Battery<o:p>

Beginning with the IBM AT, PCs supported a hardware clock settable through BIOS. It had a century bit which allowed for manually changing the century when the year 2000 happened. Most BIOS revisions created in 1995 and nearly all BIOS revisions in 1997 supported the year 2000 by setting the century bit automatically when the clock rolled past midnight, December 31, 1999.[5] Sony VAIO VGN-FZ15 Battery<o:p>

The first flash chips were attached to the ISA bus. Starting in 1997, the BIOS flash moved to the LPC bus, a functional replacement for ISA, following a new standard implementation known as "firmware hub" (FWH). In 2006, the first systems supporting a Serial Peripheral Interface (SPI) appeared, and the BIOS flash moved again. Sony VAIO VGN-FZ15G Battery<o:p>

The size of the BIOS, and the capacities of the ROM, EEPROM and other media it may be stored on, has increased over time as new features have been added to the code; BIOS versions now exist with sizes up to 16 megabytes. Some modern motherboards are including even bigger NAND Flash ROM ICs on board which are capable of storing whole compact operating system distribution like some Linux distributions. For example, some recent ASUS motherboards included SplashTop Linux embedded into their NAND Flash ROM ICs.<o:p>

Sony VAIO VGN-FZ160E Battery<o:p>

Flashing the BIOS<o:p>

In modern PCs the BIOS is stored in rewritable memory, allowing the contents to be replaced or 'rewritten'. This rewriting of the contents is sometimes termed 'flashing'. This is done by a special program, usually provided by the system's manufacturer. A file containing such contents is sometimes termed 'a BIOS image'. A BIOS might be reflashed in order to upgrade to a newer version to fix bugs or provide improved performance or to support newer hardware, or a reflashing operation might be needed to fix a damaged BIOS. Sony VAIO VGN-FZ15T Battery<o:p>

BIOS chip vulnerabilities<o:p>

An American Megatrends BIOS registering the “Intel CPU uCode Error” while doing POST, most likely a problem with the POST.<o:p>

EEPROM chips are advantageous because they can be easily updated by the user; hardware manufacturers frequently issue BIOS updates to upgrade their products, improve compatibility and remove bugs. However, this advantage had the risk that an improperly executed or aborted BIOS update could render the computer or device unusable. To avoid these situations, more recent BIOSes use a "boot block"; a portion of the BIOS which runs first and must be updated separately. This code verifies if the rest of the BIOS is intact (using hash checksums or other methods) before transferring control to it. If the boot block detects any corruption in the main BIOS, it will typically warn the user that a recovery process must be initiated by booting from removable media (floppy, CD or USB memory) so the user can try flashing the BIOS again. Some motherboards have a backup BIOS (sometimes referred to as DualBIOS boards) to recover from BIOS corruptions. Sony VAIO VGN-FZ17 Battery<o:p>

Overclocking<o:p>

Some BIOS chips allow overclocking, an action in which the CPU is adjusted to a higher clock rate than its factory preset. Overclocking may, however, seriously compromise system reliability in insufficiently cooled computers and generally shorten component lifespan.<o:p>

Virus attacks<o:p>

There are at least three known BIOS attack viruses, two of which were for demonstration purposes. Sony VAIO VGN-FZ17G Battery<o:p>

CIH<o:p>

The first was a virus which was able to erase Flash ROM BIOS content, rendering computer systems unstable. CIH, also known as "Chernobyl Virus", appeared for the first time in mid-1998 and became active in April 1999. It affected systems' BIOS's and often they could not be fixed on their own since they were no longer able to boot at all. To repair this, Flash ROM IC had to be removed from the motherboard to be reprogrammed elsewhere. Damage from CIH was possible since the virus was specifically targeted at the then widespread Intel i430TX motherboard chipset, and the most common operating systems of the time were based on the Windows 9x family allowing direct hardware access to all programs. Sony VAIO VGN-FZ18 Battery<o:p>

Modern systems are not vulnerable to CIH because of a variety of chipsets being used which are incompatible with the Intel i430TX chipset, and also other Flash ROM IC types. There is also extra protection from accidental BIOS rewrites in the form of boot blocks which are protected from accidental overwrite or dual and quad BIOS equipped systems which may, in the event of a crash, use a backup BIOS. Also, all modern operating systems like Linux, Mac OS X, Windows NT-based Windows OS like Windows 2000, Windows XP and newer, do not allow user mode programs to have direct hardware access. As a result, as of 2008, CIH has become essentially harmless, at worst causing annoyance by infecting executable files and triggering alerts from antivirus software. Other BIOS viruses remain possible, however[6]: since most Windows users run all applications with administrative privileges, a modern CIH-like virus could in principle still gain access to hardware. Sony VAIO VGN-FZ180E Battery<o:p>

Black Hat 2006<o:p>

The second one was a technique presented by John Heasman, principal security consultant for UK based Next-Generation Security Software at the Black Hat Security Conference (2006), where he showed how to elevate privileges and read physical memory, using malicious procedures that replaced normal ACPI functions stored in flash memory. Sony VAIO VGN-FZ180E/B Battery<o:p>

Persistent BIOS Infection<o:p>

The third one, known as "Persistent BIOS infection", was a method presented in CanSecWest Security Conference (Vancouver, 2009) and SyScan Security Conference (Singapore, 2009) where researchers Anibal Sacco [7] and Alfredo Ortega, from Core Security Technologies, demonstrated insertion of malicious code into the decompression routines in the BIOS, allowing for nearly full control of the PC at every start-up, even before the operating system is booted. Sony VAIO VGN-FZ18E Battery<o:p>

The proof-of-concept does not exploit a flaw in the BIOS implementation, but only involves the normal BIOS flashing procedures. Thus, it requires physical access to the machine or for the user on the operating system to be root. Despite this, however, researchers underline the profound implications of their discovery: “We can patch a driver to drop a fully working rootkit. We even have a little code that can remove or disable antivirus.”[8] Sony VAIO VGN-FZ18G Battery<o:p>

Firmware on adapter cards<o:p>

A computer system can contain several BIOS firmware chips. The motherboard BIOS typically contains code to access hardware components absolutely necessary for bootstrapping the system, such as the keyboard (either PS/2 or on a USB human interface device), and storage (floppy drives, if available, and IDE or SATA hard disk controllers). In addition, plug-in adapter cards such as SCSI, RAID, Network interface cards, and video boards often include their own BIOS (e.g. Video BIOS), complementing or replacing the system BIOS code for the given component. (This code is generally referred to as an option ROM.) Even devices built into the motherboard can behave in this way; their option ROMs can be stored as separate code on the main BIOS flash chip, and upgraded either in tandem with, or separately to, the main BIOS. Sony VAIO VGN-FZ18M Battery<o:p>

An add-in card usually only requires an option ROM if it:<o:p>

Needs to be used before the operating system can be loaded (usually this means it is required in the bootstrapping process), and<o:p>

Is too sophisticated or specific a device to be handled by the main BIOS<o:p>

Older PC operating systems, such as MS-DOS (including all DOS-based versions of Microsoft Windows), and early-stage bootloaders, may continue to use the BIOS for input and output. However, the restrictions of the BIOS environment means that modern OSes will almost always use their own device drivers to directly control the hardware. Generally, these device drivers only use BIOS and option ROM calls for very specific (non-performance-critical) tasks, such as preliminary device initialization. Sony VAIO VGN-FZ18T Battery<o:p>

In order to discover memory-mapped option ROMs during the boot process, PC BIOS implementations scan real memory from 0xC0000 to 0xF0000 on 2 KiB boundaries, looking for a ROM signature: 0xAA55 (0x55 followed by 0xAA, since the x86 architecture is little-endian). In a valid expansion ROM, this signature is immediately followed by a single byte indicating the number of 512-byte blocks it occupies in real memory. The next byte contains an offset describing the option ROM's entry point, to which the BIOS immediately transfers control. At this point, the expansion ROM code takes over, using BIOS services to register interrupt vectors for use by post-boot applications, provide a user configuration interface, or display diagnostic information. Sony VAIO VGN-FZ190 Battery<o:p>

There are many methods and utilities for examining the contents of various motherboard BIOS and expansion ROMs, such as Microsoft DEBUG or the UNIX dd.<o:p>

BIOS boot specification<o:p>

If the expansion ROM wishes to change the way the system boots (such as from a network device or a SCSI adapter for which the BIOS has no driver code), it can use the BIOS Boot Specification (BBS) API to register its ability to do so. Once the expansion ROMs have registered using the BBS APIs, the user can select among the available boot options from within the BIOS's user interface. This is why most BBS compliant PC BIOS implementations will not allow the user to enter the BIOS's user interface until the expansion ROMs have finished executing and registering themselves with the BBS API.[citation needed] Sony VAIO VGN-FZ190E/1 BatteryChanging role of the BIOS<o:p>

Some operating systems, for example MS-DOS, rely on the BIOS to carry out most input/output tasks within the PC.[9] A variety of technical reasons makes it inefficient for some recent operating systems written for 32-bit CPUs such as Linux and Microsoft Windows to invoke the BIOS directly. Larger, more powerful, servers and workstations using PowerPC or SPARC CPUs by several manufacturers developed a platform-independent Open Firmware (IEEE-1275), based on the Forth programming language. It is included with Sun's SPARC computers, IBM's RS/6000 line, and other PowerPC CHRP motherboards. Later x86-based personal computer operating systems, like Windows NT, use their own, native drivers which also makes it much easier to extend support to new hardware, while the BIOS still relies on a legacy 16-bit runtime interface. Sony VAIO VGN-FZ190E/2 Battery<o:p>

There was a similar transition for the Apple Macintosh, where the system software originally relied heavily on the ToolBox—a set of drivers and other useful routines stored in ROM based on Motorola's 680x0 CPUs. These Apple ROMs were replaced by Open Firmware in the PowerPC Macintosh, then EFI in Intel Macintosh computers.<o:p>

Later BIOS took on more complex functions, by way of interfaces such as ACPI; these functions include power management, hot swapping and thermal management. However BIOS limitations (16-bit processor mode, only 1 MiB addressable space, PC AT hardware dependencies, etc.) were seen as clearly unacceptable for the newer computer platforms. Extensible Firmware Interface (EFI) is a specification which replaces the runtime interface of the legacy BIOS. Initially written for the Itanium architecture, EFI is now available for x86 and x86-64 platforms; the specification development is driven by The Unified EFI Forum, an industry Special Interest Group. Sony VAIO VGN-FZ190E/B Battery<o:p>

<o:p> 

Linux has supported EFI via the elilo boot loader. The Open Source community increased their effort to develop a replacement for proprietary BIOSes and their future incarnations with an open sourced counterpart through the coreboot and OpenBIOS/Open Firmware projects. AMD provided product specifications for some chipsets, and Google is sponsoring the project. Motherboard manufacturer Tyan offers coreboot next to the standard BIOS with their Opteron line of motherboards. MSI and Gigabyte Technology have followed suit with the MSI K9ND MS-9282 and MSI K9SD MS-9185 resp. the M57SLI-S4 models. Sony VAIO VGN-FZ190N2 Battery<o:p>

Some BIOSes contain a "SLIC", a digital signature placed inside the BIOS by the manufacturer, for example Dell. This SLIC is inserted in the ACPI table and contains no active code. Computer manufacturers that distribute OEM versions of Microsoft Windows and Microsoft application software can use the SLIC to authenticate licensing to the OEM Windows Installation disk and/or system recovery disc containing Windows software. Systems having a SLIC can be activated with an OEM Product Key, and they verify an XML formatted OEM certificate against the SLIC in the BIOS as a means of self-activating. If a user performs a fresh install of Windows, they will need to have possession of both the OEM key and the digital certificate for their SLIC in order to bypass activation; in practice this is extremely unlikely and hence the only real way this can be achieved is if the user performs a restore using a pre-customised image provided by the OEM. Sony VAIO VGN-FZ190N3 Battery<o:p>

edit]The BIOS business<o:p>

The vast majority of PC motherboard suppliers license a BIOS "core" and toolkit from a commercial third-party, known as an "independent BIOS vendor" or IBV. The motherboard manufacturer then customizes this BIOS to suit its own hardware. For this reason, updated BIOSes are normally obtained directly from the motherboard manufacturer.<o:p>

Major BIOS vendors include American Megatrends (AMI), Insyde Software, Phoenix Technologies and Byosoft. Former vendors include Award Software and Microid Research which were acquired by Phoenix Technologies in 1998. Phoenix has now phased out the Award Brand name. General Software, which was also acquired by Phoenix in 2007, sold BIOS for Intel processor based embedded systems.BootingSony VAIO VGN-FZ190N5 Battery<o:p>

Boot(2)<o:p>

This article includes a list of references, but its sources remain unclear because it has insufficient inline citations.<o:p>

Please help to improve this article by introducing more precise citations where appropriate. (October 2008)<o:p>

In computing, booting (also known as "booting up") is a bootstrapping process that starts operating systems when the user turns on a computer system. A boot sequence is the initial set of operations that the computer performs when power is switched on. The bootloader typically loads the main operating system for the computer. Sony VAIO VGN-FZ19VN Battery<o:p>

The computer word boot is short for "bootstrap" (itself short for "bootstrap load"). The term bootstrap derives from the idiom pull oneself up by one's bootstraps.[1] The term refers to the fact that a computer cannot run without first loading software but must be running before any software can be loaded, which seems as impossible as to "pull yourself up by your own bootstraps."[2] Sony VAIO VGN-FZ21E Battery<o:p>

In computers in the 1950s, pressing a bootstrap button caused a hardwired program to read a bootstrap program from a punched card and then execute the loaded boot program, which loaded a larger system of programs from punched cards into memory without further help from the human operator.[3][4] The term "boot" has been used in this sense since at least 1958.[5]<o:p>

The CDC 6600 (c. 1964) had a dead start panel with 144 toggle switches; the dead start switch entered 12 words from the toggle switches to the memory of peripheral processor (PP) 0 and initiated the load sequence. PP 0 loaded the necessary code into its own memory and then initialized the other PP's. Sony VAIO VGN-FZ21J Battery<o:p>

The GE 645 (c. 1965) had a "BOOT" button.[6] It is possible that the contraction from "bootstrap" to "boot" was motivated by an inclination to label the button with fewer, larger characters, or the contraction may follow the familiar habit of contracting words to make them easier to say, and to create insider jargon.<o:p>

Some machines, like the Atari ST microcomputer, were "instant-on" with the operating system executing from a ROM. Retrieval of the OS from secondary or tertiary store was thus eliminated as one of the characteristic operations for bootstrapping. To accommodate system customization for loading accessories and other support software automatically, as part of the boot process, the Atari's floppy drive was read for the additional components. There was a timeout delay, allowing time to manually insert a floppy, as the system searched for the extra components, which could be avoided by inserting a blank disk. Sony VAIO VGN-FZ21M Battery<o:p>

The Multics operating system (c. 1967) had a boot command.[7][8] Multics documents also refer to "boot tapes," but it is hard to determine exactly when that term was first used.<o:p>

In the Unix operating system, the earliest reference for "boot" is probably in The Unix Programmer's Manual, first edition 1971.11.03.[9] Sony VAIO VGN-FZ21S Battery<o:p>

The bootstrap concept was used in the IBM 701 computer (1952–1956) which had a "load button" ["load" button?] which initiated reading of the first 36-bit word from a punched card in a card reader, or from a magnetic tape unit, or magnetic drum unit (predecessor of the magnetic hard disk drive). The left 18-bit half-word was then executed as an instruction which read additional words into memory.[10] Sony VAIO VGN-FZ21Z Battery<o:p>

Boot loader<o:p>

A computer's central processor can only execute program code found in Read-Only Memory (ROM), Random Access Memory (RAM) or an operator's console. Modern operating systems and application program code and data are stored on nonvolatile data storage devices, such as hard disk drives, CD, DVD, flash memory cards (like an SD card), USB flash drive, and floppy disk. When a computer is first powered on, it does not have an operating system in ROM or RAM. The computer must initially execute a small program stored in ROM along with the bare minimum of data needed to access the nonvolatile devices from which the operating system programs and data are loaded into RAM. Sony VAIO VGN-FZ25 Battery<o:p>

The small program that starts this sequence of loading into RAM, is known as a bootstrap loader, bootstrap or boot loader. This small boot loader program's only job is to load other data and programs which are then executed from RAM. Often, multiple-stage boot loaders are used, during which several programs of increasing complexity sequentially load one after the other in a process of chain loading.<o:p>

Early computers (such as the IBM 650, DEC PDP-1 through PDP-8 and early models of the PDP-11) had a row of dials or toggle switches on the front panel to allow the operator to manually enter the boot instructions into memory before transferring control to the CPU, or to directly pass an instruction to the CPU. The boot loader would then read in either the second-stage boot loader (called Binary Loader of paper tape with checksum), or the operating system from an outside storage medium such as paper tape, punched card, or a disk drive. Sony VAIO VGN-FZ250E/B Battery<o:p>

Pseudo-assembly code for the bootloader might be as simple as the following eight instructions:<o:p>

Set the P register to 8<o:p>

Check paper tape reader ready<o:p>

If not ready, jump to 1<o:p>

Read a byte from paper tape reader to accumulator<o:p>

If end of tape, jump to 8<o:p>

Store accumulator to address in P register<o:p>

Increment the P register<o:p>

Jump to 1<o:p>

A related example is based on a loader for a 1970's Nicolet Instrument Corporation minicomputer. Note that the bytes of the second-stage loader are read from paper tape in reverse order.<o:p>

Set the P register to 106<o:p>

Check paper tape reader ready<o:p>

If not ready, jump to 1<o:p>

Read a byte from paper tape reader to accumulator<o:p>

Store accumulator to address in P register<o:p>

Decrement the P register<o:p>

Jump to 1<o:p>

The length of the second stage loader is such that the final byte overwrites location 6. After the instruction in location 5 executes, location 6 starts the second stage loader executing. The second stage loader then waits for the much longer tape containing the operating system to be placed in the tape reader. The difference between the boot loader and second stage loader is the addition of checking code to trap paper tape read errors, a frequent occurrence with the hardware of the time, which in this case was an ASR-33 teletype. Sony VAIO VGN-FZ27 Battery<o:p>

Some computer systems, upon receiving a boot signal from a human operator or a peripheral device, may load a very small number of fixed instructions into memory at a specific location, initialize at least one CPU, and then point the CPU to the instructions and start their execution. These instructions typically start an input operation from some peripheral device (which may be switch-selectable by the operator). Other systems may send hardware commands directly to peripheral devices or I/O controllers that cause an extremely simple input operation (such as "read sector zero of the system device into memory starting at location 1000") to be carried out, effectively loading a small number of bootload instructions into memory; a completion signal from the I/O device may then be used to start execution of the instructions by the CPU. Sony VAIO VGN-FZ28 Battery<o:p>

Smaller computers often use less flexible but more automatic bootload mechanisms to ensure that the computer starts quickly and with a predetermined software configuration. In many desktop computers, for example, the bootstrapping process begins with the CPU executing software contained in ROM (for example, the BIOS of an IBM PC) at a predefined address (some CPUs, including the Intel x86 series are designed to execute this software after reset without outside help). This software contains rudimentary functionality to search for devices eligible to participate in booting, and load a small program from a special section (most commonly the boot sector) of the most promising device. Sony VAIO VGN-FZ280E/B Battery<o:p>

Boot loaders may face peculiar constraints, especially in size; for instance, on the IBM PC and compatibles, the first stage of boot loaders located on hard drives must fit into the first 446 bytes (or 440 bytes if Windows NT or above has to be supported because NT put 6 byte disk-signature starting from offset 440) of the Master Boot Record, in order to leave room for the 64-byte partition table and the 2-byte 0xAA55 'signature', which the BIOS requires for a proper boot loader. Sony VAIO VGN-FZ290 Battery<o:p>

Some operating systems, most notably pre-1995 Macintosh systems from Apple, are so closely interwoven with their hardware that it is impossible to natively boot an operating system other than the standard one. This is the opposite extreme of the bootload using switches mentioned above; it is highly inflexible but relatively error-proof and foolproof as long as all hardware is working normally. A common solution in such situations is to design a bootloader that works as a program belonging to the standard OS that hijacks the system and loads the alternative OS. This technique was used by Apple for its A/UX Unix implementation and copied by various freeware operating systems and BeOS Personal Edition 5. Sony VAIO VGN-FZ290EAB Battery<o:p>

The Atari ST also had its operating system in ROM but, by inserting the Spectre GCR cartridge with the Macintosh system ROM in the game slot and turning the Atari on, it could "natively boot" the Macintosh operating system rather than Atari's own TOS system. The Atari ST hardware was designed so the cartridge slot could provide native program execution for gaming purposes as a holdover from Atari's legacy making electronic games. Sony VAIO VGN-FZ290EBB Battery<o:p>