Updated program with command line checking included.

The elementary C program we were working with is now updated with a little bit of command line checking.

#include<stdio.h>

int addnumbers(int num_1, int num_2)
{
   int sum = 0;
   sum = num_1 + num_2;
   return sum;
}

int subnumbers(int num_1, int num_2)
{

 int subtrt =0;
 subtrt = num_1 - num_2;
 return subtrt;
}

int main(int argc, char **argv)
{
  if (argc < 2)
     {
     printf("Correct usage: tst2 <1st number> <2nd number>\n");
     return 0;
     }
  else
     {
     int num_1 = atoi(argv[1]);
     int num_2 = atoi(argv[2]);

     printf("\n\n Welcome to simple add and subtract program\n\n\n");
     printf("Sum of %d + %d = %d\n\n", num_1, num_2, addnumbers(num_1, num_2));
     printf("Difference of %d - %d = %d\n\n",num_1, num_2,subnumbers(num_1, num_2));
     getchar();
     return 0;
     }
}