Printing with the 0( zero ) flag fills in leading zeros : printf 0s « printf scanf « C Tutorial

1. C Tutorial
2. printf scanf
3. printf 0s

#include <stdio.h>

int main()
{ 
   printf( "%+09d\n", 452 );
   printf( "%09d\n", 452 );

   return 0;

}

+00000452
000000452