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<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
<html xmlns="http://www.w3.org/1999/xhtml"><head><title>thunk</title><link rel="stylesheet" href="../../jargon.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.61.0"/><link rel="home" href="../index.html" title="The Jargon File"/><link rel="up" href="../T.html" title="T"/><link rel="previous" href="thundering-herd-problem.html" title="thundering herd problem"/><link rel="next" href="tick.html" title="tick"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">thunk</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="thundering-herd-problem.html">Prev</a> </td><th width="60%" align="center">T</th><td width="20%" align="right"> <a accesskey="n" href="tick.html">Next</a></td></tr></table><hr/></div><dt><a id="thunk"/><dt xmlns="" id="thunk"><b>thunk</b>: <span xmlns="http://www.w3.org/1999/xhtml" class="pronunciation">/thuhnk/</span>, <span xmlns="http://www.w3.org/1999/xhtml" class="grammar">n.</span></dt></dt><dd><p> 1. [obs.]&#8220;<span class="quote">A piece of coding which provides an
address:</span>&#8221;, 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 which
computes the expression and leaves the address of the result in some
standard location. </p></dd><dd><p> 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 <span class="firstterm">closure</span>). The
process of unfreezing these thunks is called <span class="firstterm">forcing</span>. </p></dd><dd><p> 3. A <a href="../S/stubroutine.html"><i class="glossterm">stubroutine</i></a>, in an overlay programming
environment, that loads and jumps to the correct overlay. Compare
<a href="trampoline.html"><i class="glossterm">trampoline</i></a>.</p></dd><dd><p>4. Microsoft and IBM have both defined, in their Intel-based
systems, a &#8220;<span class="quote">16-bit environment</span>&#8221; (with bletcherous segment
registers and 64K address limits) and a &#8220;<span class="quote">32-bit environment</span>&#8221;
(with flat addressing and semi-real memory management). The two
environments can both be running on the same computer and OS (thanks to
what is called, in the Microsoft world, WOW which stands for Windows On
Windows). MS and IBM have both decided that the process of getting from 16-
to 32-bit and vice versa is called a &#8220;<span class="quote">thunk</span>&#8221;; for Windows 95,
there is even a tool THUNK.EXE called a &#8220;<span class="quote">thunk compiler</span>&#8221;.
</p></dd><dd><p> 5. A person or activity scheduled in a thunklike manner. &#8220;<span class="quote">It
occurred to me the other day that I am rather accurately modeled by a thunk
&#8212; I frequently need to be forced to completion.:</span>&#8221; &#8212;
paraphrased from a <a href="../P/plan-file.html"><i class="glossterm">plan file</i></a>.</p></dd><dd><p>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 suggests 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
&#8216;already been thought of&#8217;; thus it was christened a <span class="firstterm">thunk</span>, which is &#8220;<span class="quote">the past tense of
&#8216;think&#8217; at two in the morning</span>&#8221;.</p></dd><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="thundering-herd-problem.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="../T.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="tick.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">thundering herd problem </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> tick</td></tr></table></div></body></html>