Question

char again;
do {
            counter = 0;
            while (counter < 3) {
               printf("Please enter a number: ");
               scanf("%d", &num);
               counter++;
               sum += num;
            }
            if (counter == 3) {
                printf("Would you like to continue? [Y]Yes [N]No:");
                scanf("%c", &again);
            } 
        }while (again == 'Y');

I can’t seem to figure out why this won’t work. If i enter Y it breaks, if I enter N it breaks. I need to loop until the user enters “N” to exit the program and no other letter.

Answer 1

Change the scanf call to:

scanf(" %c", &again);

The trick is in the space before the %c: it instructs the scanf function to ignore any whitespace character before returning your N or Y. Otherwise you will be reading the return carriages from the previous scanf calls.

From man 3p scanf (the POSIX one):

A directive composed of one or more white-space characters shall be executed by reading input until no more valid input can be read, or up to the
first byte which is not a white-space character, which remains unread.

That is a complex function. I recommend reading the man page with care: it can do much more than most people think.