rand, srand - random number generator
#include <stdlib.h>
void srand(unsigned seed)
unsigned rand(void)
Rand uses a multiplicative congruential random number generator with
period 2**32 to return successive pseudo-random numbers in the range from
0 to RAND_MAX.
The generator is reinitialized by calling srand with 1 as argument. It
can be set to a random starting point by calling srand with whatever you
like as argument.
random(3).