Undocumented feature
Encyclopedia
Undocumented features are frequently found in computer software
releases. Sometimes the documentation is omitted through simple oversight, but undocumented features are often elements of the software not intended for use by end users, but left available for use by the vendor for software support
and development.
Since the suppliers of the software usually consider the software documentation
to constitute a contract for the behavior of the software, undocumented features are generally left unsupported, and may be removed or changed at will and without notice to the users. This makes using undocumented features a double-edged sword.
Sometimes such a feature (for example, the ability to change the switch character in MS-DOS
, usually to a hyphen
) is included for compatibility
(in this case with Unix
utilities) or future-expansion reasons, but the software provider changes their mind or goes out of business; the absence of documentation makes it easier to justify the feature's removal.
New versions of software might omit mention of old (possibly superseded) features in documentation but keep them implemented for users who've grown accustomed to them.
In other cases, software bug
s are referred to jokingly as undocumented features. ("It's not a bug; it's an undocumented feature!") This usage may have been popularised in some of Microsoft's responses to bug reports for its first "Word for Windows" product. (James Gleick, What Just Happened, ch.1), but doesn't originate there. The first reference on Usenet
that survives dates to 5 March 1984. Between 1969 and 1972, Sandy Mathes, a systems programmer for PDP-8
software at Digital Equipment Corporation
(DEC) in Maynard, MA, used the terms "bug" and "feature" in her reporting of test results to distinguish between undocumented actions of delivered software products that were unacceptable and tolerable, respectively. This usage may have been perpetuated.
Ironically, undocumented features themselves have become a major feature of computer games
. Developers often include various cheats and other special features ("easter eggs
") that are not explained in the packaged material, but have become part of the "buzz" about the game on the Internet
and among gamers. The undocumented features of foreign games are often elements that were not localized from their native language.
Closed source API
s can also have undocumented functions that are not generally known. These are sometimes used to gain a commercial advantage over 3rd-party software by providing additional information or better performance to the application provider.
Computer software
Computer software, or just software, is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do it....
releases. Sometimes the documentation is omitted through simple oversight, but undocumented features are often elements of the software not intended for use by end users, but left available for use by the vendor for software support
Help desk
A help desk is an information and assistance resource that troubleshoots problems with computers or similar products. Corporations often provide help desk support to their customers via a toll-free number, website and e-mail. There are also in-house help desks geared toward providing the same kind...
and development.
Since the suppliers of the software usually consider the software documentation
Software documentation
Software documentation or source code documentation is written text that accompanies computer software. It either explains how it operates or how to use it, and may mean different things to people in different roles....
to constitute a contract for the behavior of the software, undocumented features are generally left unsupported, and may be removed or changed at will and without notice to the users. This makes using undocumented features a double-edged sword.
Sometimes such a feature (for example, the ability to change the switch character in MS-DOS
MS-DOS
MS-DOS 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...
, usually to a hyphen
Hyphen
The hyphen is a punctuation mark used to join words and to separate syllables of a single word. The use of hyphens is called hyphenation. The hyphen should not be confused with dashes , which are longer and have different uses, or with the minus sign which is also longer...
) is included for compatibility
Computer compatibility
A family of computer models is said to be compatible if certain software that runs on one of the models can also be run on all other models of the family. The computer models may differ in performance, reliability or some other characteristic...
(in this case with Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
utilities) or future-expansion reasons, but the software provider changes their mind or goes out of business; the absence of documentation makes it easier to justify the feature's removal.
New versions of software might omit mention of old (possibly superseded) features in documentation but keep them implemented for users who've grown accustomed to them.
In other cases, software bug
Software bug
A software bug is the common term used to describe an error, flaw, mistake, failure, or fault in a computer program or system that produces an incorrect or unexpected result, or causes it to behave in unintended ways. Most bugs arise from mistakes and errors made by people in either a program's...
s are referred to jokingly as undocumented features. ("It's not a bug; it's an undocumented feature!") This usage may have been popularised in some of Microsoft's responses to bug reports for its first "Word for Windows" product. (James Gleick, What Just Happened, ch.1), but doesn't originate there. The first reference on Usenet
Usenet
Usenet is a worldwide distributed Internet discussion system. It developed from the general purpose UUCP architecture of the same name.Duke University graduate students Tom Truscott and Jim Ellis conceived the idea in 1979 and it was established in 1980...
that survives dates to 5 March 1984. Between 1969 and 1972, Sandy Mathes, a systems programmer for PDP-8
PDP-8
The 12-bit PDP-8 was the first successful commercial minicomputer, produced by Digital Equipment Corporation in the 1960s. DEC introduced it on 22 March 1965, and sold more than 50,000 systems, the most of any computer up to that date. It was the first widely sold computer in the DEC PDP series of...
software at Digital Equipment Corporation
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
(DEC) in Maynard, MA, used the terms "bug" and "feature" in her reporting of test results to distinguish between undocumented actions of delivered software products that were unacceptable and tolerable, respectively. This usage may have been perpetuated.
Ironically, undocumented features themselves have become a major feature of computer games
Computer Games
"Computer Games" is a single by New Zealand group, Mi-Sex released in 1979 in Australia and New Zealand and in 1981 throughout Europe. It was the single that launched the band, and was hugely popular, particularly in Australia and New Zealand...
. Developers often include various cheats and other special features ("easter eggs
Easter egg (media)
Image:Carl Oswald Rostosky - Zwei Kaninchen und ein Igel 1861.jpg|250px|thumb|right|Example of Easter egg hidden within imagerect 467 383 539 434 desc none...
") that are not explained in the packaged material, but have become part of the "buzz" about the game on the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
and among gamers. The undocumented features of foreign games are often elements that were not localized from their native language.
Closed source API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
s can also have undocumented functions that are not generally known. These are sometimes used to gain a commercial advantage over 3rd-party software by providing additional information or better performance to the application provider.
See also
- Backdoor (computing)
- Easter egg (media)Easter egg (media)Image:Carl Oswald Rostosky - Zwei Kaninchen und ein Igel 1861.jpg|250px|thumb|right|Example of Easter egg hidden within imagerect 467 383 539 434 desc none...
- Undocumented instructionIllegal opcodeAn Illegal Opcode, also called an Undocumented Instruction, is an instruction to a CPU that is not mentioned in any official documentation released by the CPU's designer or manufacturer, which nevertheless has an effect. Illegal opcodes were common on older CPUs designed during the 1970s, such as...