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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102/clib/rand.c

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+/* 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 */
+}
+