srand

Defined in header `<stdlib.h>`
void srand( unsigned seed );

Seeds the pseudo-random number generator used by rand() with the value seed.

If rand() is used before any calls to srand(), rand() behaves as if it was seeded with srand(1).

Each time rand() is seeded with the same seed, it must produce the same sequence of values.

srand() is not guaranteed to be thread-safe.