An undocumented feature is an unintended or undocumented hardware operation, for example an undocumented instruction, or software feature found in computer hardware and software that is considered beneficial or useful. 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. Also, some unintended operation of hardware or software that ends up being of utility to users is simply a bug, flaw or quirk.
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.
Undocumented or unsupported features are sometimes also called "not manufacturer supported" (NOMAS), a term coined by PPC Journal in the early 1980s.[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.[5]
PPC_1983 was invoked but never defined (see the help page).Zenrom_1984 was invoked but never defined (see the help page).PPC_1985 was invoked but never defined (see the help page).Wright_2023 was invoked but never defined (see the help page).Carr_2018 was invoked but never defined (see the help page).