:unixism: n. A piece of code or a coding technique that depends on the protected multi-tasking environment with relatively low process-spawn overhead that exists on virtual-memory UNIX systems. Common {unixism}s include: gratuitous use of `fork(2)'; the assumption that certain undocumented but well-known features of UNIX libraries such as `stdio(3)' are supported elsewhere; reliance on {obscure} side-effects of system calls (use of `sleep(2)' with a 0 argument to clue the scheduler that you're willing to give up your time-slice, for example); the assumption that freshly allocated memory is zeroed; and the assumption that fragmentation problems won't arise from never `free()'ing memory. Compare {vaxocentrism}; see also {New Jersey}.

:unleaded: adj. Said of decaffeinated coffee, diet coke, and other
imitation {programming fluid}s. "Do you want regular or
unleaded?". Appears to be widespread among programmers associated
with the oil industry in Texas (and probably elsewhere). Usage:
silly, and probably unintelligable to the next generation of
hackers.

:unroll: v. To repeat the body of a loop several times in succession.
This optimization technique reduces the number of times the
loop-termination test has to be executed. But it only works if
the number of iterations desired is a multiple of the number of
repetitions of the body. Something has to be done to take care
of any leftover iterations —- such as {Duff's device}.

:unswizzle: v. See {swizzle}.

:unwind the stack: vi. 1. [techspeak] During the execution of a procedural language, one is said to `unwind the stack' from a called procedure up to a caller when one discards the stack frame and any number of frames above it, popping back up to the level of the given caller. In C this is done with `longjmp'/`setjmp', in LISP with `throw/catch'. See also {smash the stack}. 2. People can unwind the stack as well, by quickly dealing with a bunch of problems: "Oh heck, let's do lunch. Just a second while I unwind my stack."

:unwind-protect: [MIT: from the name of a LISP operator] n. A task you must remember to perform before you leave a place or finish a project. "I have an unwind-protect to call my advisor."

:up: adj. 1. Working, in order. "The down escalator is up." Oppose {down}. 2. `bring up': vt. To create a working version and start it. "They brought up a down system." 3. `come up' vi. To become ready for production use.

:upload: /uhp'lohd/ v. 1. [techspeak] To transfer programs or data over a digital communications link from a smaller or peripheral `client' system to a larger or central `host' one. A transfer in the other direction is, of course, called a {download} (but see the note about ground-to-space comm under that entry). 2. [speculatively] To move the essential patterns and algorithms that make up one's mind from one's brain into a computer. Only those who are convinced that such patterns and algorithms capture the complete essence of the self view this prospect with gusto.

:upthread: adv. Earlier in the discussion (see {thread}), i.e., `above'. "As Joe pointed out upthread, …" See also {followup}.

:urchin: n. See {munchkin}.