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.