Undocumented feature

Sometimes the documentation is omitted through oversight, but undocumented features are sometimes not intended for use by end users, but left available for use by the vendor for software support and development.

[1][2][3][4] Some user-reported defects are viewed by software developers as working as expected, leading to the catchphrase "it's not a bug, it's a feature" (INABIAF) and its variations.

Video game and demoscene programmers have taken advantage of the unintended operation of computers' hardware to produce new effects or optimizations.

Undocumented features (for example, the ability to change the switch character in MS-DOS, usually to a hyphen) can be included for compatibility purposes (in this case with Unix utilities) or for future-expansion reasons.

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.