isocRandEx.c

/**
   @file      isocRandEx.c
   @author    Mitch Richling <http://www.mitchr.me/>
   @Copyright Copyright 1998 by Mitch Richling.  All rights reserved.
   @brief     hello   @EOL
   @Keywords  iso c random rand srand
   @Std       C89

              The random number generators implemented to meet the ISO
              C standard are almost always very primitive.  ISO C
              doesn't specify the algorithm to use for the generation
              of the sequence, but most implementations are a simple
              linear congruence generator.  The standard specifies
              that the maximum random number possible must be at least
              2**17.  Sequences generated by rand() are almost always
              very poor and are not suitable for serious simulation
              work.  Even the minimal standard random number generator
              is better --- and given the ease with which the minimal
              standard can be implemented one really has no reason not
              to use it.  Still, rand() is always around and ready for
              use.

              While non-standard, many UNIX implementations provide
              for a function sranddev() that uses the random device to
              set the seed for rand().  I think this function appeared
              sometime around BSD 4.2.
              
*/

#include <stdio.h>              /* I/O lib         ISOC  */
#include <stdlib.h>             /* Standard Lib    ISOC  */

int main(int argc, char *argv[]);

int main(int argc, char *argv[]) {

  int i, aRand;

  printf("Biggest rand: %lu\n", (unsigned long)RAND_MAX);

  /* Set the seed for the random number -- use an unsigned integer */
  srand(1234);

  printf("Five random integers in U[0, RAND_MAX]\n");
  for(i=0; i<5; i++) {
    aRand = rand();
    printf("%3d %15d\n", i, aRand);
  }

  return 0;
}