The New Hacker's Dictionary

Historical note: at MIT this usage has traditionally been traced to the programming language MAD (Michigan Algorithm Decoder), an Algol-58-like language that was the most common choice among mainstream (non-hacker) users at MIT in the mid-60s. It inherited from Algol-58 a control structure FOR VALUES OF X = 3, 7, 99 DO ... that would repeat the indicated instructions for each value in the list (unlike the usual FOR that only works for arithmetic sequences of values). MAD is long extinct, but similar for-constructs still flourish (e.g., in Unix's shell languages).

fora // pl. n.

Plural of forum.

foreground // vt.

[Unix; common] To bring a task to the top of one's stack for immediate processing, and hackers often use it in this sense for non-computer tasks. "If your presentation is due next week, I guess I'd better foreground writing up the design document."

Technically, on a time-sharing system, a task executing in foreground is one able to accept input from and return output to the user; oppose background. Nowadays this term is primarily associated with Unix, but it appears first to have been used in this sense on OS/360. Normally, there is only one foreground task per terminal (or terminal window); having multiple processes simultaneously reading the keyboard is a good way to lose.

fork //

In the open-source community, a fork is what occurs when two (or more) versions of a software package's source code are being developed in parallel which once shared a common code base, and these multiple versions of the source code have irreconcilable differences between them. This should not be confused with a development branch, which may later be folded back into the original source code base. Nor should it be confused with what happens when a new distribution of Linux or some other distribution is created, because that largely assembles pieces than can and will be used in other distributions without conflict.

Forking is uncommon; in fact, it is so uncommon that individual instances loom large in hacker folklore. Notable in this class were the http://www.xemacs.org/About/XEmacsVsGNUemacs.html, the GCC/EGCS fork (later healed by a merger) and the forks among the FreeBSD, NetBSD, and OpenBSD operating systems.

fork bomb // n.

[Unix] A particular species of wabbit that can be written in one line of C (main() {for(;;)fork();}) or shell ($0 & $0 &) on any Unix system, or occasionally created by an egregious coding bug. A fork bomb process 'explodes' by recursively spawning copies of itself (using the Unix system call fork(2)). Eventually it eats all the process table entries and effectively wedges the system. Fortunately, fork bombs are relatively easy to spot and kill, so creating one deliberately seldom accomplishes more than to bring the just wrath of the gods down upon the perpetrator. See also logic bomb.