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Digital-Research-Source-Code/CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102/clib/rand.c
Sepp J Morris 31738079c4 Upload
Digital Research
2020-11-06 18:50:37 +01:00

36 lines
593 B
C

/* rand.c - kluges a random number generator with addition & overflow */
#include <portab.h>
#define NSEEDS 7
MLOCAL UWORD _seeds[NSEEDS] =
{ 0, 24213, 12345, 4622, 2143, 32010, 7942 };
MLOCAL WORD _seedptr=0;
WORD srand(seed1)
int seed1;
{
WORD ncs;
_seeds[0] = seed1;
for( ncs = seed1&077; ncs; ncs-- )
rand();
return(rand());
}
WORD rand()
{
UWORD tot, ii;
for( tot=0, ii=0; ii<NSEEDS; ii++)
tot += _seeds[ii]; /* ignore overflow */
if( ++_seedptr >= NSEEDS )
_seedptr = 0;
_seeds[_seedptr] = tot;
return( tot >> 1 ); /* ignore lo bit because of addition */
}