int rand([int min], [int max]);If called without the optional min,max arguments rand() returns a pseudo-random value between 0 and RAND_MAX. If you want a random number between 5 and 15 (inclusive), for example, use rand(5,15).
Remember to seed the random number generator before use with srand().
See also srand(), getrandmax(), mt_rand(), mt_srand() and mt_getrandmax().