C/Console/Console Input Validation

Force user to enter a valid response

<source lang="cpp">

1. include <stdio.h>

int main(void) {

 int a, b;
 char ch;
 printf("Do you want to (Choose the first letter):\n");
 printf("(A)dd, (S)ubtract, (M)ultiply, or (D)ivide?\n");
 do {
   printf("Choice: ");
   ch = getchar();
 } while(ch!="A" && ch!="S" && ch!="M" && ch!="D");
 printf("\n");
 printf("Enter first number: ");
 scanf("%d", &a);
 
 printf("Enter second number: ");
 scanf("%d", &b);
 if(ch=="A") 
     printf("%d", a + b);
 else if(ch=="S") 
     printf("%d", a - b);
 else if(ch=="M") 
     printf("%d", a * b);
 else if(ch=="D" && b!=0) 
     printf("%d", a / b);
 return 0;

}

      </source>