Why do I always get the same sequence of random numbers with rand()?

Question

This is the first time I\'m trying random numbers with C (I miss C#). Here is my code:

int i, j = 0;
for(i = 0; i <= 10; i++) {
    j = rand();
    printf         


        

Answer 1

Random number generators are not actually random, they like most software is completely predictable. What rand does is create a different pseudo-random number each time it is called One which appears to be random. In order to use it properly you need to give it a different starting point.

#include 
#include 
#include 

int main ()
{
  /* initialize random seed: */
  srand ( time(NULL) );

  printf("random number %d\n",rand());
  printf("random number %d\n",rand());
  printf("random number %d\n",rand());
  printf("random number %d\n",rand());

  return 0;
}