Accept uppercase and lowercase character

Question

I’m making a draft just to train the if and the else which will be subject in my next class in college. I want to get there and at least already have a basis of what the teacher will teach.

My question is this:.

When I ask the user to type s (Yes) or n (No) to show the tab works, but if the user type the S uppercase letter IDE executes block else.

How do I make the user only type uppercase letters on printf?

Follow the code below.

#include <stdio.h>
#include <stdlib.h>

main(){

  int num;
  char sn;
  printf("DESEJA ABRIR A TABUADA? S/N: ");
  scanf("%c", &sn);

  if(sn=='s') {
        printf("\nDIGITE O NUMERO DA TABUADA QUE DESEJA: ");
        scanf("%d", &num);
        printf("\n%d x 1 = %d\n", num , num*1);
        printf("%d x 2 = %d\n", num , num*2);
        printf("%d x 3 = %d\n", num , num*3);
        printf("%d x 4 = %d\n", num , num*4);
        printf("%d x 5 = %d\n", num , num*5);
        printf("%d x 6 = %d\n", num , num*6);
        printf("%d x 7 = %d\n", num , num*7);
        printf("%d x 8 = %d\n", num , num*8);
        printf("%d x 9 = %d\n", num , num*9);
        printf("%d x 10 = %d\n\n", num , num*10); 
  }

  else
       printf("\nOK, PROGRAMA FINALIZADO.\n\n");

  system("pause");

}

Answer 1

• You can use the function toupper and convert the sn uppercase then put something like :

  if(sn=='S')

Thus, if the user writes s will convert to S, write S maintains. That is, this way you can either write in uppercase or lowercase.

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• Another way would be to put the operator || (OR)

  if(sn=='S' || sn=='s')// sn igual a S OU sn igual a s

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P.S. User will not type in printf, the scanf is reading what the user writes.