bignum

/big'nuhm/ [orig. from MIT MacLISP] n. 1. [techspeak] A multiple-precision computer representation for very large integers. 2. More generally, any very large number. "Have you ever looked at the United States Budget? There's bignums for you!" 3. [Stanford] In backgammon, large numbers on the dice especially a roll of double fives or double sixes (compare moby, sense 4). See also El Camino Bignum.

Sense 1 may require some explanation. Most computer languages provide a kind of data called `integer', but such computer integers are usually very limited in size; usually they must be smaller than than 2^(31) (2,147,483,648) or (on a bitty box) 2^(15) (32,768). If you want to work with numbers larger than that, you have to use floating-point numbers, which are usually accurate to only six or seven decimal places. Computer languages that provide bignums can perform exact calculations on very large numbers, such as 1000! (the factorial of 1000, which is 1000 times 999 times 998 times ... times 2 times 1). For example, this value for 1000! was computed by the MacLISP system using bignums: 

     40238726007709377354370243392300398571937486421071
     46325437999104299385123986290205920442084869694048
     00479988610197196058631666872994808558901323829669
     94459099742450408707375991882362772718873251977950
     59509952761208749754624970436014182780946464962910
     56393887437886487337119181045825783647849977012476
     63288983595573543251318532395846307555740911426241
     74743493475534286465766116677973966688202912073791
     43853719588249808126867838374559731746136085379534
     52422158659320192809087829730843139284440328123155
     86110369768013573042161687476096758713483120254785
     89320767169132448426236131412508780208000261683151
     02734182797770478463586817016436502415369139828126
     48102130927612448963599287051149649754199093422215
     66832572080821333186116811553615836546984046708975
     60290095053761647584772842188967964624494516076535
     34081989013854424879849599533191017233555566021394
     50399736280750137837615307127761926849034352625200
     01588853514733161170210396817592151090778801939317
     81141945452572238655414610628921879602238389714760
     88506276862967146674697562911234082439208160153780
     88989396451826324367161676217916890977991190375403
     12746222899880051954444142820121873617459926429565
     81746628302955570299024324153181617210465832036786
     90611726015878352075151628422554026517048330422614
     39742869330616908979684825901254583271682264580665
     26769958652682272807075781391858178889652208164348
     34482599326604336766017699961283186078838615027946
     59551311565520360939881806121385586003014356945272
     24206344631797460594682573103790084024432438465657
     24501440282188525247093519062092902313649327349756
     55139587205596542287497740114133469627154228458623
     77387538230483865688976461927383814900140767310446
     64025989949022222176590433990188601856652648506179
     97023561938970178600408118897299183110211712298459
     01641921068884387121855646124960798722908519296819
     37238864261483965738229112312502418664935314397013
     74285319266498753372189406942814341185201580141233
     44828015051399694290153483077644569099073152433278
     28826986460278986432113908350621709500259738986355
     42771967428222487575867657523442202075736305694988
     25087968928162753848863396909959826280956121450994
     87170124451646126037902930912088908694202851064018
     21543994571568059418727489980942547421735824010636
     77404595741785160829230135358081840096996372524230
     56085590370062427124341690900415369010593398383577
     79394109700277534720000000000000000000000000000000
     00000000000000000000000000000000000000000000000000
     00000000000000000000000000000000000000000000000000
     00000000000000000000000000000000000000000000000000
     00000000000000000000000000000000000000000000000000
     000000000000000000.