Question

At http://www.cplusplus.com/reference/clibrary/cstdlib/rand/ , I read the following : This algorithm uses a seed to generate the series, which should be initialized to some distinctive value using srand.

What does seed mean and how does rand() use seed to generate the series?

Answer 1

Very crudely, it is something like:

   int rand() {
       return last_random_val = 
          ((last_random_val * 1103515245) + 12345) & 0x7fffffff);
   }

   void srand(int seed) {
        last_random_val = seed;
   }

And the last_random_val is set to the seed when you call srand(). Hence, for the same seed, same sequence of numbers are generated.