Backward compatibility in the context of Real mode

Ethernet (/ˈiːθərnɛt/ EE-thər-net) is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. Ethernet has since been refined to support higher bit rates, a greater number of nodes, and longer link distances, but retains much backward compatibility. Over time, Ethernet has largely replaced competing wired LAN technologies such as Token Ring, FDDI and ARCNET.

The original 10BASE5 Ethernet uses a thick coaxial cable as a shared medium. This was largely superseded by 10BASE2, which used a thinner and more flexible cable that was both less expensive and easier to use. More modern Ethernet variants use twisted pair and fiber optic links in conjunction with switches. Over the course of its history, Ethernet data transfer rates have been increased from the original 2.94 Mbit/s to the latest 800 Gbit/s, with rates up to 1.6 Tbit/s under development. The Ethernet standards include several wiring and signaling variants of the OSI physical layer.

In computing, a Unicode symbol is a Unicode character which is not part of a script used to write a natural language, but is nonetheless available for use as part of a text.

Many of the symbols are drawn from existing character sets or ISO/IEC or other national and international standards. The Unicode Standard states that "The universe of symbols is rich and open-ended," but that in order to be considered, a symbol must have a "demonstrated need or strong desire to exchange in plain text." This makes the issue of what symbols to encode and how symbols should be encoded more complicated than the issues surrounding writing systems. Unicode focuses on symbols that make sense in a one-dimensional plain-text context. For example, the typical two-dimensional arrangement of electronic diagram symbols justifies their exclusion. (Legacy characters such as box-drawing characters, Symbols for Legacy Computing and the Symbols for Legacy Computing Supplement, are an exception, since these symbols largely exist for backward compatibility with past encoding systems; a number of electronic diagram symbols are indeed encoded in Unicode's Miscellaneous Technical block.) For adequate treatment in plain text, symbols must also be displayable in a monochromatic setting. Even with these limitations – monochromatic, one-dimensional and standards-based – the domain of potential Unicode symbols is extensive. (However, emojis – ideograms, graphic symbols – that were admitted into Unicode, allow colors although the colors are not standardized. Color-dependent emojis are traditionally rendered using hatching in monochromatic settings.)

The Nintendo DS is a foldable handheld game console produced by Nintendo, released worldwide between 2004 and 2005. The "DS" in the name is an initialism for "Developers' System" or "Dual Screen", reflecting the system’s most distinctive feature: two LCD screens working in tandem, with the lower screen functioning as a touchscreen. Both screens are housed in a clamshell design similar to that of the Game Boy Advance SP and some models of the Game & Watch series. The Nintendo DS supported wireless connectivity for local multiplayer over short distances, as well as online play through the now-defunct Nintendo Wi-Fi Connection service. During the seventh generation of video game consoles, its primary competitor was Sony's PlayStation Portable.

Prior to release, Nintendo marketed the DS as an experimental "third pillar" in its console lineup, intended to complement the Game Boy Advance family and the GameCube. However, backward compatibility with Game Boy Advance titles and strong sales led it to be widely regarded as the successor to the Game Boy line. On March 2, 2006, Nintendo released the Nintendo DS Lite, a slimmer and lighter redesign featuring brighter screens and improved battery life. The system was later followed by the Nintendo DSi, released on November 1, 2008, which introduced additional enhancements such as dual digital cameras and digital distribution of games, while removing backward compatibility with Game Boy Advance titles.

Camlp4 is a software system for writing extensible parsers for programming languages. It provides a set of OCaml libraries that are used to define grammars as well as loadable syntax extensions of such grammars. Camlp4 stands for Caml Preprocessor and Pretty-Printer and one of its most important applications was the definition of domain-specific extensions of the syntax of OCaml.

Camlp4 was part of the official OCaml distribution which is developed at the INRIA. Its original author is Daniel de Rauglaudre. OCaml version 3.10.0, released in May 2007, introduced a significantly modified and backward-incompatible version of Camlp4. De Rauglaudre maintains a separate backward-compatible version, which has been renamed Camlp5. All of the examples below are for Camlp5 or the previous version of Camlp4 (versions 3.09 and prior).

The Game Boy Color (abbreviated as GBC or CGB) is an 8-bit handheld game console developed by Nintendo. It was released in Japan on October 21, 1998, and in international markets the following month. Compared with the original Game Boy, the Game Boy Color features a color TFT screen instead of monochrome, a CPU running at up to twice the speed, and four times as much memory. It is backward compatible with games developed for its predecessor. The Game Boy Color was released during the fifth generation of video game consoles and competed with the WonderSwan and Neo Geo Pocket, and Genesis Nomad.

The handheld is slightly thicker, taller and has a smaller screen than its immediate predecessor, the Game Boy Pocket, but is significantly smaller than the original Game Boy. As with its predecessors, the Game Boy Color has a custom 8-bit processor made by Sharp. The American English spelling of the system's name, Game Boy Color, remains consistent throughout the world.

A bell character (sometimes bell code) is a device control code originally sent to ring a small electromechanical bell on tickers and other teleprinters and teletypewriters to alert operators at the other end of the line, often of an incoming message. Though tickers punched the bell codes into their tapes, printers generally do not print a character when the bell code is received. Bell codes are usually represented by the label BEL. They have been used since 1870 (initially in the Baudot code).

To maintain backward compatibility, video display terminals (VDTs) that replaced teletypewriters included speakers or buzzers to perform the same function, as did the personal computers that followed. Modern terminal emulators often integrate the warnings to the desktop environment (e.g., the macOS Terminal will play the system warning sound) and also often offer a silent visual bell feature that flashes the terminal window briefly.

The Atari 7800 ProSystem, or simply the Atari 7800, is a home video game console released by Atari Corporation in May 1986 as the successor to both the Atari 2600 and Atari 5200. It can run almost all Atari 2600 cartridges, making it the first console with backward compatibility. It shipped with a two button controller, instead of the 2600-standard Atari CX40 joystick, and with Pole Position II as the pack-in game. The European model has a gamepad instead of a joystick. Most of the early releases for the system are ports of 1981–1983 arcade video games. The final wave of 7800 cartridges is closer in style to what was available on other late 1980s consoles, such as Scrapyard Dog and Midnight Mutants.

Designed by General Computer Corporation, the 7800 has custom graphics hardware similar to early 1980s arcade video games and is a significant improvement over Atari's previous consoles. The same Television Interface Adaptor chip that launched with the Atari VCS in 1977, included for compatibility with cartridges for that system, is used to generate two-channel audio for 7800 games. In an effort to prevent the flood of poor quality games that contributed to the video game crash of 1983, cartridges had to be digitally signed by Atari.

The Zilog Z80 is an 8-bit microprocessor designed by Zilog, first released in 1976; it played an important role in the evolution of early personal computing. It was designed to be software-compatible with the Intel 8080, offering a compelling alternative due to its better integration and increased performance. Along with the 8080's seven registers and flags register, the Z80 introduced an alternate register set, two 16-bit index registers, and additional instructions, including bit manipulation and block copy/search.

Originally intended for use in embedded systems like the 8080 was, the Z80's combination of compatibility, affordability, and superior performance led to widespread adoption in video game systems and home computers throughout the late 1970s and early 1980s, helping to fuel the personal computing revolution. The Z80 was used in iconic products such as the Osborne 1, Radio Shack TRS-80, ColecoVision, ZX Spectrum, Sega's Master System and the Pac-Man arcade cabinet. In the early 1990s, it was used in portable devices, including the Game Gear and the TI-83 series of graphing calculators.

The IBM System/370 (S/370) is a range of computers, from entry-level to mainframes, announced as the successors to the System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the product announcement. Like its predecessor, the System/370 became a dominant computing platform and was a major commercial success for IBM.

Early 370 systems differed from the 360 largely in their internal circuitry, moving from the Solid Logic Technology hybrid integrated circuits containing separate transistors to more modern monolithic integrated circuits containing multiple transistors per integrated circuit, which IBM called Monolithic System Technology, or MST. The higher density packaging allowed several formerly optional features from the 360 line to be included as standard features of the machines, floating-point support for instance. The 370 also added a small number of new instructions.

The PlayStation 2 (PS2) is a home video game console developed and marketed by Sony Computer Entertainment. It was first released in Japan on 4 March 2000, in North America on October 26, in Europe on November 24, in Australia on November 30, and other regions thereafter. It is the successor to the original PlayStation as well as the second installment in the PlayStation brand of consoles. As a sixth-generation console, it competed with Nintendo's GameCube, Sega's Dreamcast, and Microsoft's Xbox.

Announced in 1999, Sony began developing the console after the immense success of its predecessor. In addition to serving as a game console, it features a built-in DVD drive and was priced lower than standalone DVD players of the time, enhancing its value. Full backward compatibility with original PlayStation games and accessories gave it access to a vast launch library, far surpassing those of its competitors. The console's hardware was also notable for its custom-built Emotion Engine processor, co-developed with Toshiba, which was promoted as being more powerful than most personal computers of the era.