Initialize random number generator.
  Uses seed parameter to set a new starting point for generating random numbers with rand.
  If seed is set to 1 the generator is reinitialized to its initial value as before any call to rand or srand.
  In order to generate true random numbers it is suggested to use as seed a value that changes often, like the one returned by time function included in <time.h> (the number of seconds elapsed since newyear 1970).

Parameters.

seed

An integer value to be used as starting point with the pseudo-random number generator algorithm.

Return Value.
  (none)

Portability.
  Defined in ANSI-C.

Example.

/* rand/srand example */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

main ()
{
  /* initialize random generator */
  srand ( time(NULL) );

  /* generate some random numbers */
  printf ("A number between 0 and 100: %d\n", rand()%100);
  printf ("A number between 20 and 30: %d\n", rand()%10+20);

  return 0;
}

See also.
  rand