As you can read from
this[
^] you need to initialize the random number generator (using the
srand function[
^]) before calling the rand function it.
Example from the reference link:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main ()
{
int iSecret, iGuess;
srand ( time(NULL) );
iSecret = rand() % 10 + 1;
do {
printf ("Guess the number (1 to 10): ");
scanf ("%d",&iGuess);
if (iSecret<iGuess) puts ("The secret number is lower");
else if (iSecret>iGuess) puts ("The secret number is higher");
} while (iSecret!=iGuess);
puts ("Congratulations!");
return 0;
}