void srand( unsigned int seed );
head file is <stdlib.h>
Remarks
The srand function sets the starting point for generating a series of pseudorandom
integers. To reinitialize the generator, use 1 as the seed argument. Any other value for
seed sets the generator to a random starting point. rand retrieves the pseudorandom
numbers that are generated. Calling rand before any call to srand generates the same
sequence as calling srand with seed passed as 1.

复制代码 代码如下:
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
void main( void )
{
   int i;
   /* Seed the random-number generator with current time so that
    * the numbers will be different every time we run.
    */
   srand((unsigned)time(NULL));
   /* Display 10 numbers. */
   for( i = 0;   i < 10;i++ )
      printf("  %6d\n", rand());
}