In technology, especially computing (irrespective of platform), a product is said to be backward compatible (or upward compatible) when it is able to take the place of an older product, by interoperating with other products that were designed for the older product. Image File history File links Question_book-3. ... By the mid 20th century humans had achieved a mastery of technology sufficient to leave the surface of the Earth for the first time and explore space. ... For the formal concept of computation, see computation. ...

Description

Backward compatibility is a relationship between two components, rather than being an attribute of just one of them. More generally, the following criteria need to be met:

• There is a defined functional interface "I".
• There is a server component "S" which provides the functionality of I.
• There is a client component "C" which depends on S via I.
• A new server component "S2" is created which has greater functionality than S and which it exposes via a new interface "I2".
• All the functions of I are also provided by I2. In other words, I is a subset of I2.

When these criteria are met, S2 is backward compatible with S because it still supports interface I and therefore the client C can be switched over to use S2 and still operate correctly.

Backward compatibility is the special case of compatibility in which the new server has a direct historical ancestral relationship with the old server. If this special relationship does not exist then it not usually spoken of as "backward" compatibility but is instead just "compatible" — a consistent interface allowing interoperability between components and products that were each developed separately.

Data does nothing in the absence of an interpreter, so the notion of compatibility does not apply to document files, it only applies to software. In the case of a program that creates document files, a new version of that program ("v2") is said to be backward compatible with the old version of the program ("v1") when it can both read and write documents that work with v1. Everything that v1 could do must also be possible with v2, including saving documents that can be read by v1. In that case, if the criteria outlined earlier are applied, the interface "I" supported by both software versions is actually their common document format. The metaphor is completed by observing that S2 is v2 and C is v1. The old version would have performed the roles of both S and C consecutively, because using v1 to open a previously saved document is functionally equivalent to v1 requesting data from an earlier instance of v1 via an interpreter interface I that both reads and writes files.

If a newer software version cannot save files that can be read by the older version it is not backward compatible with the older version, although it may provide an irreversible upgrade capability for the old files. This situation has often been used strategically by software vendors to force customers to purchase upgrades since, over time, the number of data files usable by an old version diminishes at a rate proportional to the number of other customers that have upgraded.

Levels of compatibility vary. In software, binary compatibility and source-compatibility are distinguishable. Binary compatibility means that programs can work correctly with the new version of this library without requiring recompilation. Source compatibility requires recompilation but no changes to the source code. In computing, a device (usually a computer processor) that can run the same source code intended to be compiled and run on another device is said to be source-compatible. ... A diagram of the operation of a typical multi-language, multi-target compiler. ...

Many platforms rely on emulation, the simulation of an older platform in software, to achieve backward compatibility. This article is about emulation in computer science. ...

Compatibility checking

Approaches for checking compatibility between the client program and the server component include:

• Check by version number;
• Check by an interface definition language (IDL)
• Check by just-in-time test runs (the client program gives some example inputs to the server component to see if the component returns the desired example outputs).

An interface description language, (alternatively interface definition language) (IDL), is a computer language or simple syntax for describing the interface of a software component. ...

Alternate Meaning

In certain contexts, people will sometimes refer to syntax additions or library changes that would break previous compilers or runtimes as "backward incompatible". In this case, the meaning of backward compatibility has been overloaded to mean both "new server is compatible with old input" and "old server is compatible with new input". This secondary meaning is closer to Forward compatibility, though its use is not uncommon. Forward compatibility (sometimes confused with extensibility) is the ability of a system to accept input intended for later versions of itself. ...

Examples

• A computer system is backward compatible if it is able to work with software or accessories designed for the system it is meant to replace.
  • The IBM 7080 transistorized computer was backward compatible with all models of the IBM 705 vacuum tube computer.
  • The Atari 7800 is backward compatible with most Atari 2600 games.
  • The Commodore 128 is 99% backward compatible with Commodore 64 software and hardware.
  • The Game Boy Advance line (except the Game Boy Micro) is backward compatible with previous Game Boy systems, meaning all Game Boy and Game Boy Color titles are playable on this system.
  • The PlayStation 2 is backward compatible with most of the original PlayStation library.
  • The Nintendo DS is backward compatible with Game Boy Advance games only in single-player mode.
  • The PlayStation 3 is backward compatible with many PlayStation & PlayStation 2 games. This is provided by the inclusion of the original Emotion Engine chip that is built inside the PS2. This form of compatibility is only available to the first series of consoles that launched across North America, Japan, Hong Kong and Taiwan, the later launch of the system in many PAL areas (Europe, Oceania, Asia) lacked the chip provided in the original units and instead relied on software emulation (which greatly reduced the number of playable titles) for backwards compatibility. It was announced that future versions of the console in all areas will lack the Emotion Engine with the first use of this seen in the new 80GB model. Also the new 40GB model removes PS2 compatibility altogether to lower costs but still, for unknown reasons, retains the abilty to play PS1 titles.
  • All of Intel x86 processors – Core 2, Core, Pentium 4, Pentium III, Pentium II, Pentium Pro, Pentium, 80486, 80386, 80286, 80186 and 8086 – are backward compatible with their predecessors, because they can execute programs written for an earlier processor.
  • The Xbox 360 is backward compatible with some Xbox games. This is achieved through emulation.
  • The Wii is backward compatible with all games from the previous Nintendo system, the Nintendo GameCube, due to it being based on the PowerPC, the same base as the latter. It is compatible with GameCube controllers and memory cards but not with other peripherals such as the Game Boy Player. Some games originally released for older consoles – the NES, SNES, Nintendo 64, Sega Genesis, Turbografx 16 and Neo Geo – are available to play on the Wii via emulation, however the Wii cannot be said to be backward compatible with these systems as the software in its original format (i.e. cartridges) cannot be used.
• Other examples of backward-compatible software
  • Microsoft Windows 32-bit versions contain code to be backward compatible with most software from earlier 32-bit and 16 bit versions (Example, Civilization (circa 1991, designed for Windows 3.0) running on Windows Vista). XP, Vista and Server x64 versions drop 16 bit support for reliability while maintaining 32-bit support.
  • Microsoft Word 2000 was backward compatible with Word 97 due to the fact that it could read and write files in Word 97 format, with the understanding that features unique to Word 2000 would not appear in Word 97. Same applied to Word 2002 and Word 2003.
  • By adding the proper external hardware, many consoles can become backward compatible. This includes:
    • The Atari 5200 can play Atari 2600 games by adding the "Atari VCS Cartridge Adapter".
    • The ColecoVision can play Atari 2600 games by adding the "Expansion Module #1".
    • The Intellivision can play Atari 2600 games by adding the "System Changer".
    • The Sega Genesis can play Sega Master System games by adding a "Power Base Converter".
    • The Sega Game Gear can play Sega Master System games by adding a "Master Gear".
    • The Super NES can play games for the original Game Boy by adding a "Super Game Boy" cartridge
    • The Super Nintendo Entertainment System can play games for the Nintendo Entertainment System by adding a Super 8 (video game accessory).
    • The Nintendo 64 can play games for the Nintendo Entertainment System and Super Nintendo Entertainment System by adding a Tristar 64, although this add-on was not licenced by Nintendo.
    • The Nintendo GameCube can play any existing game from the Game Boy line by adding a "Game Boy Player" add-on and disc.
  • Several computer operating systems have various methods of running software originally designed for older versions or other OSes:
    • Windows NT and successors have various subsystems to run legacy applications. MS-DOS and Win16 subsystems (only on i386) can run some applications for those platforms, and it has an OS/2 subsystem for running CLI OS/2 applications.
    • Wine can run many applications for Microsoft Windows on some Unix-like operating systems.

This article or section is in need of attention from an expert on the subject. ... The IBM 7080 was a transistorized variable word length BCD computer in the IBM 700/7000 series commercial architecture line, introduced in August 1961, that provided an upgrade path from the vacuum tube IBM 705 computer. ... Assorted discrete transistors A transistor is a semiconductor device, commonly used as an amplifier or an electrically controlled switch. ... An IBM 704 mainframe (image courtesy of LLNL) The IBM 700/7000 series was a series of large scale (mainframe) computer systems made by IBM through the 1950s and early 1960s. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... The Atari 7800 is a video game console released by Atari in June 1986 (a test market release occurred two years earlier). ... The Atari 2600, released in October 1977, is the video game console credited with popularizing the use of microprocessor based hardware and cartridges containing game code, instead of having non-microprocessor dedicated hardware with all games built in. ... The Commodore 128 (C128, CBM 128, C=128) home/personal computer was Commodore Business Machiness (CBM) last commercially released 8-bit machine. ... C-64 redirects here. ... “GBA” redirects here. ... Game Boy Micro , trademarked Game Boy micro) is a handheld game console developed and manufactured by Nintendo. ... For the entire Game Boy series of handheld consoles, see Game Boy line. ... For the entire Game Boy series of handheld consoles, see Game Boy line. ... The Game Boy Color , shortened to GBC) is Nintendos successor to the Game Boy and was released on October 21, 1998 in Japan and in November of 1998 in the United States and 1999 in Europe. ... PS2 redirects here. ... The Sony PlayStation ) is a video game console of the 32/64-bit era, first produced by Sony Computer Entertainment in the mid-1990s. ... NDS redirects here. ... “GBA” redirects here. ... The PlayStation 3 , trademarked PLAYSTATION®3,[3] commonly abbreviated PS3) is the third home video game console produced by Sony Computer Entertainment; successor to the PlayStation 2. ... The Sony PlayStation ) is a video game console of the 32/64-bit era, first produced by Sony Computer Entertainment in the mid-1990s. ... PS2 redirects here. ... Sony Emotion Engine CPU The Emotion Engine is a CPU developed and manufactured by Sony and Toshiba for use in the Sony PlayStation 2. ... North America North America is a continent [1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... For other uses, see PAL (disambiguation). ... For other uses, see Europe (disambiguation). ... For other uses, see Oceania (disambiguation). ... For other uses, see Asia (disambiguation). ... PS2 can mean: PlayStation 2 (Sony PS2), sixth-generation video game console PS/2 (IBM Personal System/2 office PCs, or the interface standard for mice and keyboards that the PS/2 series set) Phantasy Star II, second in the Phantasy Star seiries of video games. ... PS1 can mean: PlayStation 1 (Sony PSOne) PS/1 (IBM Personal System/1 series of Home PCs) PS1 (LINUX A string for shell settings to display its prompt) This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... Intel Pentium 4 (Northwood version), one example out of a huge number of x86 implementations from Intel, AMD, and others. ... The Core 2 brand refers to a range of Intels consumer 64-bit dual-core and MCM quad-core CPUs with the x86-64 instruction set, and based on the Intel Core microarchitecture, which derived from the 32-bit dual-core Yonah laptop processor. ... This article is about the Intel mobile processor family. ... The Pentium 4[1] brand refers to Intels single-core mainstream desktop and laptop CPUs introduced on November 20, 2000[2] (August 8, 2008 is the date of last shipments of Pentium 4s[3]). They had the 7th-generation architecture - called NetBurst - which was the companys first all... Pentium III logo The Pentium III is an x86 (more precisely, an i686) architecture microprocessor by Intel, introduced on February 26, 1999. ... Intel Pentium II Logo The Pentium II is an x86 architecture microprocessor by Intel, introduced on May 7, 1997. ... The Pentium Pro is a sixth-generation x86 architecture microprocessor (P6 core) produced by Intel and was originally intended to replace the original Pentium in a full range of applications, but later, was reduced to a more narrow role as a server and high-end desktop chip. ... This article does not cite any references or sources. ... The Intel486[1] brand refers to Intels family of i486 (incl. ... The Intel386[1] is a microprocessor which was used as the central processing unit (CPU) of many personal computers from 1986 until 2007. ... AMD 80286 at 12 MHz. ... An Intel 80186 Microprocessor The 80186 architecture. ... The 8086[1] is a 16-bit microprocessor chip designed by Intel in 1978, which gave rise to the x86 architecture. ... It has been suggested that Xbox 360 Elite be merged into this article or section. ... The Xbox is a sixth generation era video game console produced by Microsoft Corporation. ... The Wii (pronounced as the pronoun we, IPA: ) is the fifth home video game console released by Nintendo. ... Nintendo Company, Limited (任天堂 or ニンテンドー Nintendō; NASDAQ: NTDOY, TYO: 7974 usually referred to as simply Nintendo, or Big N ) is a multinational corporation founded on September 23, 1889[1] in Kyoto, Japan by Fusajiro Yamauchi to produce handmade hanafuda cards. ... The Nintendo GameCube (GCN) is Nintendos fourth home video game console, belonging to the sixth generation era. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... “NES” redirects here. ... The Super Nintendo Entertainment System or Super NES (also called SNES and Super Nintendo) was a 16-bit video game console released by Nintendo in North America, Europe, Australasia, and Brazil between 1990 and 1993. ... The Nintendo 64 ), often abbreviated as N64, is Nintendos third home video game console for the international market. ... The Mega Drive/Genesis was a 16-bit video game console released by Sega in Japan (1988), Europe (1990) and most of the rest of the world as the Mega Drive. ... The TurboGrafx-16, known as PC Engine （PCエンジン） in Japan, is a video game console first released in Japan by the Nippon Electric Company on October 30, 1987. ... Neo-Geo is the name of a cartridge-based arcade and home video game system released in 1990 by Japanese game company SNK. The system offered comparatively colorful 2D graphics and high-quality sound. ... This article is about emulation in computer science. ... Windows redirects here. ... For the complete series of games, see Civilization (series). ... Windows 3. ... Windows XP is a line of operating systems developed by Microsoft for use on general-purpose computer systems, including home and business desktops, notebook computers, and media centers. ... Windows Vista is a line of graphical operating systems used on personal computers, including home and business desktops, notebook computers, Tablet PCs, and media centers. ... Windows Server 2003 is a server operating system produced by Microsoft. ... Microsoft Word is Microsofts flagship word processing software. ... The Atari 5200 SuperSystem, or simply Atari 5200, is a video game console that was introduced in 1982 by Atari as a replacement for the famous Atari 2600. ... The Atari 2600, released in October 1977, is the video game console credited with popularizing the use of microprocessor based hardware and cartridges containing game code, instead of having non-microprocessor dedicated hardware with all games built in. ... This article does not cite any references or sources. ... The Intellivision is a video game console released by Mattel in 1979. ... The Mega Drive/Genesis was a 16-bit video game console released by Sega in Japan (1988), Europe (1990) and most of the rest of the world as the Mega Drive. ... The Sega Master System ) or SMS for short (1986 - 2000), is an 8-bit cartridge-based video game console that was manufactured by Sega. ... The Power Base Converter was an accessory made by Sega for their Genesis and Mega Drive console video game systems. ... The Sega Game Gear is a handheld game console which was Segas response to Nintendos Game Boy. ... The Sega Master System ) or SMS for short (1986 - 2000), is an 8-bit cartridge-based video game console that was manufactured by Sega. ... The Super Nintendo Entertainment System or Super NES (also called SNES and Super Nintendo) was a 16-bit video game console released by Nintendo in North America, Europe, Australasia, and Brazil between 1990 and 1993. ... For the entire Game Boy series of handheld consoles, see Game Boy line. ... Super Game Boy Box art. ... The Super Nintendo Entertainment System or Super NES (also called SNES and Super Nintendo) was a 16-bit video game console released by Nintendo in North America, Europe, Australasia, and Brazil between 1990 and 1993. ... “NES” redirects here. ... The Super 8 was an unlicensed peripheral for the Super Nintendo Entertainment System (SNES, known in Asia as the Super Famicom) video game console designed to allow the system to run games developed for the Nintendo Entertainment System (known in Asia as the Famicom). ... The Nintendo 64 ), often abbreviated as N64, is Nintendos third home video game console for the international market. ... “NES” redirects here. ... The Super Nintendo Entertainment System or Super NES (also called SNES and Super Nintendo) was a 16-bit video game console released by Nintendo in North America, Europe, Australasia, and Brazil between 1990 and 1993. ... The Tristar 64 The Tristar 64 is an unlicensed add-on for the Nintendo 64 (N64) video game console. ... The Nintendo GameCube (GCN) is Nintendos fourth home video game console, belonging to the sixth generation era. ... For the entire Game Boy series of handheld consoles, see Game Boy line. ... The Game Boy Player is a device made by Nintendo for the Nintendo GameCube which enables Game Boy (although Super Game Boy enhancements are ignored), Game Boy Color, or Game Boy Advance cartridges to be played on a television. ... An operating system (OS) is the software that manages the sharing of the resources of a computer and provides programmers with an interface used to access those resources. ... Windows NT (New Technology) is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... Windows API is a set of APIs, (application programming interfaces) available in the Microsoft Windows operating systems. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Wine is a project which aims to allow a PC with an x86 architecture processor running a Unix-like operating system and the X Window System to execute programs that were originally written for Microsoft Windows. ... Windows redirects here. ...

See also

• Forward compatibility
• Legacy system
• Enhanced remake
• Software emulation
• Computer compatibility