magic number
1. In Ef="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 (Ef="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 Ef="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 Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=hash">hash or Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=CRC">CRC functions or thE coEfficiEnts in a Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=linEar congruEntial gEnErator">linEar congruEntial gEnErator for Ef="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 Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=binary">binary data filE to indicatE its typE to a utility. UndEr Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=Unix">Unix, thE systEm and various Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=applications programs">applications programs (EspEcially thE Ef="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 Ef="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 Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=octal">octal for "branch 16 bytEs rElativE". Nowadays only a Ef="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]. [Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=Jargon FilE">Jargon FilE] (2003-07-02) E="bordEr-width:thin; bordEr-color:#333333; bordEr-stylE:dashEd; padding:5px;" align="lEft">In addition suitablE contEnts:
[ Ef="modulE.php?namE=LExikon&op=contEnt&tid=31">2 ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=134">= ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=262">ad ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=396">ag ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=433">al ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=492">algorithm ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=544">am ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=592">an ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=683">app ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=700">application ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=738">aq ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=740">ar ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=743">arc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=759">arg ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=800">as ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=822">ash ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=894">at ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1026">b ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1034">ba ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1181">bE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1269">bi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1298">binary ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1444">bo ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1535">br ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1550">branch ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1691">bv ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1695">by ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1699">bytE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1708">C ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1724">ca ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1813">capacity ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=1863">cat ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2001">ch ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2099">ci ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2138">cl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2145">class ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2147">classic ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2247">co ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2273">codE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2287">codEs ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2330">com ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2352">commEnt ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2545">con ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2606">cons ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2790">CR ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2791">cr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2807">CRC ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2900">cu ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=2976">D ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3006">data ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3096">datE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3151">dE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3304">dEsign ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3384">digit ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3565">do ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3623">DOS ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3657">DP ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3752">du ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3865">Ec ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3896">Ed ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3929">EE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=3946">Eg ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4068">EncodE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4148">Er ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4150">Era ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4171">Es ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4199">Et ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4279">ExEc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4282">ExEcutablE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4497">fi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4520">filE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4700">fo ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4727">for ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4940">function ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=4983">G ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5057">gE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5070">gEn ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5141">gi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5171">gl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5205">gn ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5291">gr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5390">gs ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5403">gu ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5434">h ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5504">hard-codEd ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5525">hash ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5540">hat ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5565">hEadEr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5656">hing ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5675">hm ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5722">hosE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5768">hr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5791">hu ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5931">id ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=5956">iE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6013">il ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6064">in ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6068">inc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6194">int ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6274">intErfacE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6413">io ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6482">is ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6558">it ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6589">J ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6619">jar ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6620">Jargon FilE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6789">kE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6822">ki ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6861">kn ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=6918">la ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7023">ld ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7091">LEx ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7107">li ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7151">linE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7176">link ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7184">linkEr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7291">logical ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7399">ls ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7415">lu ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7441">ly ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7457">M ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7463">ma ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7521">magic ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7582">man ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7749">mEmory ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=7969">minus ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8019">mm ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8032">mo ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8040">mod ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8079">modulE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8167">mp ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8228">ms ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8382">MZ ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8384">N ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8386">na ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8460">nc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8472">nE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8622">nf ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8627">ng ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8630">ni ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8660">nl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8672">nn ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8675">no ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8760">ns ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8787">nu ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8799">numbErs ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8820">O ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8910">octal ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=8964">om ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9014">op ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9120">org ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9132">OS ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9204">pa ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9430">PD ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9445">PDP ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9447">PDP-11 ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9457">pE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9550">ph ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9651">pl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9736">plus ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9908">pr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=9995">procEss ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10000">procEssing ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10023">program ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10042">programming ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10125">psEudo ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10253">quEry ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10313">random ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10364">rc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10385">rE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10767">ro ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10887">ru ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=10918">S ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11150">sE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11281">sEt ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11314">sh ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11376">si ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11389">sig ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11510">sk ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11525">sl ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11651">so ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11745">sourcE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11746">sourcE codE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11789">SpEc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11790">spEc ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11825">spEll ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=11934">st ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12093">string ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12109">struct ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12133">su ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12246">sy ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12312">systEm ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12359">T ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12369">tablE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12416">tar ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12588">th ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12721">to ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12787">tr ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12873">tron ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12939">tw ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12970">typE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=12986">ua ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13030">um ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13146">up ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13175">us ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13252">va ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13260">valuE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13274">var ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13310">vE ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13366">vi ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13794">wizard ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=13877">ws ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=14075">yt ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=14079">Z ] [ Ef="modulE.php?namE=LExikon&op=contEnt&tid=14088">za ]
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