:thumb: n. The slider on a window-system scrollbar. So called because moving it allows you to browse through the contents of a text window in a way analogous to thumbing through a book.
:thunk: /thuhnk/ n. 1. "A piece of coding which provides an address", according to P. Z. Ingerman, who invented thunks in 1961 as a way of binding actual parameters to their formal definitions in Algol-60 procedure calls. If a procedure is called with an expression in the place of a formal parameter, the compiler generates a {thunk} to compute the expression and leave the address of the result in some standard location. 2. Later generalized into: an expression, frozen together with its environment, for later evaluation if and when needed (similar to what in techspeak is called a `closure'). The process of unfreezing these thunks is called `forcing'. 3. A {stubroutine}, in an overlay programming environment, that loads and jumps to the correct overlay. Compare {trampoline}. 4. People and activities scheduled in a thunklike manner. "It occurred to me the other day that I am rather accurately modeled by a thunk —- I frequently need to be forced to completion." —- paraphrased from a {plan file}.
Historical note: There are a couple of onomatopoeic myths circulating about the origin of this term. The most common is that it is the sound made by data hitting the stack; another holds that the sound is that of the data hitting an accumulator. Yet another holds that it is the sound of the expression being unfrozen at argument-evaluation time. In fact, according to the inventors, it was coined after they realized (in the wee hours after hours of discussion) that the type of an argument in Algol-60 could be figured out in advance with a little compile-time thought, simplifying the evaluation machinery. In other words, it had `already been thought of'; thus it was christened a `thunk', which is "the past tense of `think' at two in the morning".
:tick: n. 1. A {jiffy} (sense 1). 2. In simulations, the discrete unit of time that passes between iterations of the simulation mechanism. In AI applications, this amount of time is often left unspecified, since the only constraint of interest is the ordering of events. This sort of AI simulation is often pejoratively referred to as `tick-tick-tick' simulation, especially when the issue of simultaneity of events with long, independent chains of causes is {handwave}d. 3. In the FORTH language, a single quote character.
:tick-list features: [Acorn Computers] n. Features in software or hardware that customers insist on but never use (calculators in desktop TSRs and that sort of thing). The American equivalent would be `checklist features', but this jargon sense of the phrase has not been reported.
:tickle a bug: vt. To cause a normally hidden bug to manifest through some known series of inputs or operations. "You can tickle the bug in the Paradise VGA card's highlight handling by trying to set bright yellow reverse video."
:tiger team: [U.S. military jargon] n. 1. Originally, a team whose purpose is to penetrate security, and thus test security measures. These people are paid professionals who do hacker-type tricks, e.g., leave cardboard signs saying "bomb" in critical defense installations, hand-lettered notes saying "Your codebooks have been stolen" (they usually haven't been) inside safes, etc. After a successful penetration, some high-ranking security type shows up the next morning for a `security review' and finds the sign, note, etc., and all hell breaks loose. Serious successes of tiger teams sometimes lead to early retirement for base commanders and security officers (see the {patch} entry for an example). 2. Recently, and more generally, any official inspection team or special {firefighting} group called in to look at a problem.
A subset of tiger teams are professional {cracker}s, testing the security of military computer installations by attempting remote attacks via networks or supposedly `secure' comm channels. Some of their escapades, if declassified, would probably rank among the greatest hacks of all times. The term has been adopted in commercial computer-security circles in this more specific sense.
:time sink: [poss. by analogy with `heat sink' or `current sink'] n. A project that consumes unbounded amounts of time.
:time T: /ti:m T/ n. 1. An unspecified but usually well-understood time, often used in conjunction with a later time T+1. "We'll meet on campus at time T or at Louie's at time T+1" means, in the context of going out for dinner: "We can meet on campus and go to Louie's, or we can meet at Louie's itself a bit later." (Louie's was a Chinese restaurant in Palo Alto that was a favorite with hackers.) Had the number 30 been used instead of the number 1, it would have implied that the travel time from campus to Louie's is 30 minutes; whatever time T is (and that hasn't been decided on yet), you can meet half an hour later at Louie's than you could on campus and end up eating at the same time. See also {since time T equals minus infinity}.