rand

Returns pseudorandom numbers in the range 0 to 2[31] - 1.

#include  <math.h>

int rand  (void);

This function uses the following ANSI Standard algorithm to return a random number:

static unsigned int next = 1;
int rand(void)
{
       next = next * 1103515245 + 12345;
       return (next  & RAND_MAX);
}