Answer R1

#include <stdio.h>
#include <stdlib.h>

/* Puzzle R01 -- print N random integers */

int main(int argc, char *argv[])
{
  int j;
  int limit = 25;
  unsigned int seed = 132;

  /* Use command line parameters if supplied */
  if ( argc == 3 )
  {
    limit = atoi( argv[1] );
    seed  = atoi( argv[2] );
  }

  /* Initialize the random number generator */
  srand( seed );

  for ( j=0; j < limit; j++ )
  {
    printf("%5d\n", rand() );
  }

  printf("\n"); 
  return 0;
}

Comments: Without initialization, rand() generates the same sequence of integers each time the program is run. To get a different sequence of integers, initialize rand():

  srand( seed )

The seed is an unsigned int. Every time rand() is initialized with the same seed, it will generate the same sequence of integers. Another way to initialize the generator is:

  srand( time(NULL) )

This method uses the function time(NULL) which returns the number of elapsed seconds since January first, 1970. This will be a different number each time the program is run, so rand() will be initialized differently each time, and each run of the program will use a different sequence of random integers.