magic number
1. In ref="module.php?name=Lexikon&file=search&eid=1&query=source code">source code, some non-obvious constant whose value is significant to the operation of a program and that is inserted inconspicuously in-line (ref="module.php?name=Lexikon&file=search&eid=1&query=hard-coded">hard-coded), rather than expanded in by a symbol set by a commented "#define". Magic numbers in this sense are bad style. 2. A number that encodes critical information used in an ref="module.php?name=Lexikon&file=search&eid=1&query=algorithm">algorithm in some opaque way. The classic examples of these are the numbers used in ref="module.php?name=Lexikon&file=search&eid=1&query=hash">hash or ref="module.php?name=Lexikon&file=search&eid=1&query=CRC">CRC functions or the coefficients in a ref="module.php?name=Lexikon&file=search&eid=1&query=linear congruential generator">linear congruential generator for ref="module.php?name=Lexikon&file=search&eid=1&query=pseudo-random">pseudo-random numbers. This sense actually predates, and was ancestral to, the more common sense 1. 3. Special data located at the beginning of a ref="module.php?name=Lexikon&file=search&eid=1&query=binary">binary data file to indicate its type to a utility. Under ref="module.php?name=Lexikon&file=search&eid=1&query=Unix">Unix, the system and various ref="module.php?name=Lexikon&file=search&eid=1&query=applications programs">applications programs (especially the ref="module.php?name=Lexikon&file=search&eid=1&query=linker">linker) distinguish between types of executable file by looking for a magic number. Once upon a time, these magic numbers were ref="module.php?name=Lexikon&file=search&eid=1&query=PDP-11">PDP-11 branch instructions that skipped over header data to the start of executable code 0407, for example, was ref="module.php?name=Lexikon&file=search&eid=1&query=octal">octal for "branch 16 bytes relative". Nowadays only a ref="module.php?name=Lexikon&file=search&eid=1&query=wizard">wizard knows the spells to create magic numbers. {MS DOS} executables begin with the magic string "MZ". *The* magic number, on the other hand, is 7+/-2. The paper cited below established the number of distinct items (such as numeric digits) that humans can hold in short-term memory. Among other things, this strongly influenced the interface design of the phone system. ["The magical number seven, plus or minus two: some limits on our capacity for processing information", George Miller, in the "Psychological Review" 63:81-97, 1956]. [ref="module.php?name=Lexikon&file=search&eid=1&query=Jargon File">Jargon File] (2003-07-02) In addition suitable contents:
[ ref="module.php?name=Lexikon&op=content&tid=31">2 ] [ ref="module.php?name=Lexikon&op=content&tid=134">= ] [ ref="module.php?name=Lexikon&op=content&tid=262">ad ] [ ref="module.php?name=Lexikon&op=content&tid=396">ag ] [ ref="module.php?name=Lexikon&op=content&tid=433">al ] [ ref="module.php?name=Lexikon&op=content&tid=492">algorithm ] [ ref="module.php?name=Lexikon&op=content&tid=544">am ] [ ref="module.php?name=Lexikon&op=content&tid=592">an ] [ ref="module.php?name=Lexikon&op=content&tid=683">app ] [ ref="module.php?name=Lexikon&op=content&tid=700">application ] [ ref="module.php?name=Lexikon&op=content&tid=738">aq ] [ ref="module.php?name=Lexikon&op=content&tid=740">ar ] [ ref="module.php?name=Lexikon&op=content&tid=743">arc ] [ ref="module.php?name=Lexikon&op=content&tid=759">arg ] [ ref="module.php?name=Lexikon&op=content&tid=800">as ] [ ref="module.php?name=Lexikon&op=content&tid=822">ash ] [ ref="module.php?name=Lexikon&op=content&tid=894">at ] [ ref="module.php?name=Lexikon&op=content&tid=1026">b ] [ ref="module.php?name=Lexikon&op=content&tid=1034">ba ] [ ref="module.php?name=Lexikon&op=content&tid=1181">be ] [ ref="module.php?name=Lexikon&op=content&tid=1269">bi ] [ ref="module.php?name=Lexikon&op=content&tid=1298">binary ] [ ref="module.php?name=Lexikon&op=content&tid=1444">bo ] [ ref="module.php?name=Lexikon&op=content&tid=1535">br ] [ ref="module.php?name=Lexikon&op=content&tid=1550">branch ] [ ref="module.php?name=Lexikon&op=content&tid=1691">bv ] [ ref="module.php?name=Lexikon&op=content&tid=1695">by ] [ ref="module.php?name=Lexikon&op=content&tid=1699">byte ] [ ref="module.php?name=Lexikon&op=content&tid=1708">C ] [ ref="module.php?name=Lexikon&op=content&tid=1724">ca ] [ ref="module.php?name=Lexikon&op=content&tid=1813">capacity ] [ ref="module.php?name=Lexikon&op=content&tid=1863">cat ] [ ref="module.php?name=Lexikon&op=content&tid=2001">ch ] [ ref="module.php?name=Lexikon&op=content&tid=2099">ci ] [ ref="module.php?name=Lexikon&op=content&tid=2138">cl ] [ ref="module.php?name=Lexikon&op=content&tid=2145">class ] [ ref="module.php?name=Lexikon&op=content&tid=2147">classic ] [ ref="module.php?name=Lexikon&op=content&tid=2247">co ] [ ref="module.php?name=Lexikon&op=content&tid=2273">code ] [ ref="module.php?name=Lexikon&op=content&tid=2287">codes ] [ ref="module.php?name=Lexikon&op=content&tid=2330">com ] [ ref="module.php?name=Lexikon&op=content&tid=2352">comment ] [ ref="module.php?name=Lexikon&op=content&tid=2545">con ] [ ref="module.php?name=Lexikon&op=content&tid=2606">cons ] [ ref="module.php?name=Lexikon&op=content&tid=2790">CR ] [ ref="module.php?name=Lexikon&op=content&tid=2791">cr ] [ ref="module.php?name=Lexikon&op=content&tid=2807">CRC ] [ ref="module.php?name=Lexikon&op=content&tid=2900">cu ] [ ref="module.php?name=Lexikon&op=content&tid=2976">D ] [ ref="module.php?name=Lexikon&op=content&tid=3006">data ] [ ref="module.php?name=Lexikon&op=content&tid=3096">date ] [ ref="module.php?name=Lexikon&op=content&tid=3151">de ] [ ref="module.php?name=Lexikon&op=content&tid=3304">design ] [ ref="module.php?name=Lexikon&op=content&tid=3384">digit ] [ ref="module.php?name=Lexikon&op=content&tid=3565">do ] [ ref="module.php?name=Lexikon&op=content&tid=3623">DOS ] [ ref="module.php?name=Lexikon&op=content&tid=3657">DP ] [ ref="module.php?name=Lexikon&op=content&tid=3752">du ] [ ref="module.php?name=Lexikon&op=content&tid=3865">ec ] [ ref="module.php?name=Lexikon&op=content&tid=3896">ed ] [ ref="module.php?name=Lexikon&op=content&tid=3929">ee ] [ ref="module.php?name=Lexikon&op=content&tid=3946">eg ] [ ref="module.php?name=Lexikon&op=content&tid=4068">encode ] [ ref="module.php?name=Lexikon&op=content&tid=4148">er ] [ ref="module.php?name=Lexikon&op=content&tid=4150">era ] [ ref="module.php?name=Lexikon&op=content&tid=4171">es ] [ ref="module.php?name=Lexikon&op=content&tid=4199">et ] [ ref="module.php?name=Lexikon&op=content&tid=4279">exec ] [ ref="module.php?name=Lexikon&op=content&tid=4282">executable ] [ ref="module.php?name=Lexikon&op=content&tid=4497">fi ] [ ref="module.php?name=Lexikon&op=content&tid=4520">file ] [ ref="module.php?name=Lexikon&op=content&tid=4700">fo ] [ ref="module.php?name=Lexikon&op=content&tid=4727">for ] [ ref="module.php?name=Lexikon&op=content&tid=4940">function ] [ ref="module.php?name=Lexikon&op=content&tid=4983">G ] [ ref="module.php?name=Lexikon&op=content&tid=5057">ge ] [ ref="module.php?name=Lexikon&op=content&tid=5070">gen ] [ ref="module.php?name=Lexikon&op=content&tid=5141">gi ] [ ref="module.php?name=Lexikon&op=content&tid=5171">gl ] [ ref="module.php?name=Lexikon&op=content&tid=5205">gn ] [ ref="module.php?name=Lexikon&op=content&tid=5291">gr ] [ ref="module.php?name=Lexikon&op=content&tid=5390">gs ] [ ref="module.php?name=Lexikon&op=content&tid=5403">gu ] [ ref="module.php?name=Lexikon&op=content&tid=5434">h ] [ ref="module.php?name=Lexikon&op=content&tid=5504">hard-coded ] [ ref="module.php?name=Lexikon&op=content&tid=5525">hash ] [ ref="module.php?name=Lexikon&op=content&tid=5540">hat ] [ ref="module.php?name=Lexikon&op=content&tid=5565">header ] [ ref="module.php?name=Lexikon&op=content&tid=5656">hing ] [ ref="module.php?name=Lexikon&op=content&tid=5675">hm ] [ ref="module.php?name=Lexikon&op=content&tid=5722">hose ] [ ref="module.php?name=Lexikon&op=content&tid=5768">hr ] [ ref="module.php?name=Lexikon&op=content&tid=5791">hu ] [ ref="module.php?name=Lexikon&op=content&tid=5931">id ] [ ref="module.php?name=Lexikon&op=content&tid=5956">ie ] [ ref="module.php?name=Lexikon&op=content&tid=6013">il ] [ ref="module.php?name=Lexikon&op=content&tid=6064">in ] [ ref="module.php?name=Lexikon&op=content&tid=6068">inc ] [ ref="module.php?name=Lexikon&op=content&tid=6194">int ] [ ref="module.php?name=Lexikon&op=content&tid=6274">interface ] [ ref="module.php?name=Lexikon&op=content&tid=6413">io ] [ ref="module.php?name=Lexikon&op=content&tid=6482">is ] [ ref="module.php?name=Lexikon&op=content&tid=6558">it ] [ ref="module.php?name=Lexikon&op=content&tid=6589">J ] [ ref="module.php?name=Lexikon&op=content&tid=6619">jar ] [ ref="module.php?name=Lexikon&op=content&tid=6620">Jargon File ] [ ref="module.php?name=Lexikon&op=content&tid=6789">ke ] [ ref="module.php?name=Lexikon&op=content&tid=6822">ki ] [ ref="module.php?name=Lexikon&op=content&tid=6861">kn ] [ ref="module.php?name=Lexikon&op=content&tid=6918">la ] [ ref="module.php?name=Lexikon&op=content&tid=7023">ld ] [ ref="module.php?name=Lexikon&op=content&tid=7091">Lex ] [ ref="module.php?name=Lexikon&op=content&tid=7107">li ] [ ref="module.php?name=Lexikon&op=content&tid=7151">line ] [ ref="module.php?name=Lexikon&op=content&tid=7176">link ] [ ref="module.php?name=Lexikon&op=content&tid=7184">linker ] [ ref="module.php?name=Lexikon&op=content&tid=7291">logical ] [ ref="module.php?name=Lexikon&op=content&tid=7399">ls ] [ ref="module.php?name=Lexikon&op=content&tid=7415">lu ] [ ref="module.php?name=Lexikon&op=content&tid=7441">ly ] [ ref="module.php?name=Lexikon&op=content&tid=7457">M ] [ ref="module.php?name=Lexikon&op=content&tid=7463">ma ] [ ref="module.php?name=Lexikon&op=content&tid=7521">magic ] [ ref="module.php?name=Lexikon&op=content&tid=7582">man ] [ ref="module.php?name=Lexikon&op=content&tid=7749">memory ] [ ref="module.php?name=Lexikon&op=content&tid=7969">minus ] [ ref="module.php?name=Lexikon&op=content&tid=8019">mm ] [ ref="module.php?name=Lexikon&op=content&tid=8032">mo ] [ ref="module.php?name=Lexikon&op=content&tid=8040">mod ] [ ref="module.php?name=Lexikon&op=content&tid=8079">module ] [ ref="module.php?name=Lexikon&op=content&tid=8167">mp ] [ ref="module.php?name=Lexikon&op=content&tid=8228">ms ] [ ref="module.php?name=Lexikon&op=content&tid=8382">MZ ] [ ref="module.php?name=Lexikon&op=content&tid=8384">N ] [ ref="module.php?name=Lexikon&op=content&tid=8386">na ] [ ref="module.php?name=Lexikon&op=content&tid=8460">nc ] [ ref="module.php?name=Lexikon&op=content&tid=8472">ne ] [ ref="module.php?name=Lexikon&op=content&tid=8622">nf ] [ ref="module.php?name=Lexikon&op=content&tid=8627">ng ] [ ref="module.php?name=Lexikon&op=content&tid=8630">ni ] [ ref="module.php?name=Lexikon&op=content&tid=8660">nl ] [ ref="module.php?name=Lexikon&op=content&tid=8672">nn ] [ ref="module.php?name=Lexikon&op=content&tid=8675">no ] [ ref="module.php?name=Lexikon&op=content&tid=8760">ns ] [ ref="module.php?name=Lexikon&op=content&tid=8787">nu ] [ ref="module.php?name=Lexikon&op=content&tid=8799">numbers ] [ ref="module.php?name=Lexikon&op=content&tid=8820">O ] [ ref="module.php?name=Lexikon&op=content&tid=8910">octal ] [ ref="module.php?name=Lexikon&op=content&tid=8964">om ] [ ref="module.php?name=Lexikon&op=content&tid=9014">op ] [ ref="module.php?name=Lexikon&op=content&tid=9120">org ] [ ref="module.php?name=Lexikon&op=content&tid=9132">OS ] [ ref="module.php?name=Lexikon&op=content&tid=9204">pa ] [ ref="module.php?name=Lexikon&op=content&tid=9430">PD ] [ ref="module.php?name=Lexikon&op=content&tid=9445">PDP ] [ ref="module.php?name=Lexikon&op=content&tid=9447">PDP-11 ] [ ref="module.php?name=Lexikon&op=content&tid=9457">pe ] [ ref="module.php?name=Lexikon&op=content&tid=9550">ph ] [ ref="module.php?name=Lexikon&op=content&tid=9651">pl ] [ ref="module.php?name=Lexikon&op=content&tid=9736">plus ] [ ref="module.php?name=Lexikon&op=content&tid=9908">pr ] [ ref="module.php?name=Lexikon&op=content&tid=9995">process ] [ ref="module.php?name=Lexikon&op=content&tid=10000">processing ] [ ref="module.php?name=Lexikon&op=content&tid=10023">program ] [ ref="module.php?name=Lexikon&op=content&tid=10042">programming ] [ ref="module.php?name=Lexikon&op=content&tid=10125">pseudo ] [ ref="module.php?name=Lexikon&op=content&tid=10253">query ] [ ref="module.php?name=Lexikon&op=content&tid=10313">random ] [ ref="module.php?name=Lexikon&op=content&tid=10364">rc ] [ ref="module.php?name=Lexikon&op=content&tid=10385">re ] [ ref="module.php?name=Lexikon&op=content&tid=10767">ro ] [ ref="module.php?name=Lexikon&op=content&tid=10887">ru ] [ ref="module.php?name=Lexikon&op=content&tid=10918">S ] [ ref="module.php?name=Lexikon&op=content&tid=11150">se ] [ ref="module.php?name=Lexikon&op=content&tid=11281">set ] [ ref="module.php?name=Lexikon&op=content&tid=11314">sh ] [ ref="module.php?name=Lexikon&op=content&tid=11376">si ] [ ref="module.php?name=Lexikon&op=content&tid=11389">sig ] [ ref="module.php?name=Lexikon&op=content&tid=11510">sk ] [ ref="module.php?name=Lexikon&op=content&tid=11525">sl ] [ ref="module.php?name=Lexikon&op=content&tid=11651">so ] [ ref="module.php?name=Lexikon&op=content&tid=11745">source ] [ ref="module.php?name=Lexikon&op=content&tid=11746">source code ] [ ref="module.php?name=Lexikon&op=content&tid=11789">Spec ] [ ref="module.php?name=Lexikon&op=content&tid=11790">spec ] [ ref="module.php?name=Lexikon&op=content&tid=11825">spell ] [ ref="module.php?name=Lexikon&op=content&tid=11934">st ] [ ref="module.php?name=Lexikon&op=content&tid=12093">string ] [ ref="module.php?name=Lexikon&op=content&tid=12109">struct ] [ ref="module.php?name=Lexikon&op=content&tid=12133">su ] [ ref="module.php?name=Lexikon&op=content&tid=12246">sy ] [ ref="module.php?name=Lexikon&op=content&tid=12312">system ] [ ref="module.php?name=Lexikon&op=content&tid=12359">T ] [ ref="module.php?name=Lexikon&op=content&tid=12369">table ] [ ref="module.php?name=Lexikon&op=content&tid=12416">tar ] [ ref="module.php?name=Lexikon&op=content&tid=12588">th ] [ ref="module.php?name=Lexikon&op=content&tid=12721">to ] [ ref="module.php?name=Lexikon&op=content&tid=12787">tr ] [ ref="module.php?name=Lexikon&op=content&tid=12873">tron ] [ ref="module.php?name=Lexikon&op=content&tid=12939">tw ] [ ref="module.php?name=Lexikon&op=content&tid=12970">type ] [ ref="module.php?name=Lexikon&op=content&tid=12986">ua ] [ ref="module.php?name=Lexikon&op=content&tid=13030">um ] [ ref="module.php?name=Lexikon&op=content&tid=13146">up ] [ ref="module.php?name=Lexikon&op=content&tid=13175">us ] [ ref="module.php?name=Lexikon&op=content&tid=13252">va ] [ ref="module.php?name=Lexikon&op=content&tid=13260">value ] [ ref="module.php?name=Lexikon&op=content&tid=13274">var ] [ ref="module.php?name=Lexikon&op=content&tid=13310">ve ] [ ref="module.php?name=Lexikon&op=content&tid=13366">vi ] [ ref="module.php?name=Lexikon&op=content&tid=13794">wizard ] [ ref="module.php?name=Lexikon&op=content&tid=13877">ws ] [ ref="module.php?name=Lexikon&op=content&tid=14075">yt ] [ ref="module.php?name=Lexikon&op=content&tid=14079">Z ] [ ref="module.php?name=Lexikon&op=content&tid=14088">za ]
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