Thread: scanf problem

I'm used to use the functions getche() or getch() for accepting choices for menus, and I tried to experiment using scanf(). The program example below works fine if I enter an integer, but when I entered any other keys (i.e. A-z) that's not a number, the program crashes. I tried to use isdigit() and isalpha() to detect the error and correct it--but to no avail.

Code:

#include <stdio.h>
#include <conio.h>

int main() {
    int choice;
    do {
        clrscr();
        printf("Binary and Decimal numbers\n\n");
        printf("What do you want to do?\n1. Convert Decimal to Binary\n");
        printf("2. Convert Binary to Decimal\n3. or Exit this program\n");
        printf("Enter number of choice: ");
        scanf("%d", &choice);
        switch(choice) {
            case 1:
                printf("1");
                break;
            case 2:
                printf("2");
                break;
            case 3:
                break;
            default:
                printf("Invalid choice!");
                choice = 0; // trying to replace a non-integer input but won't work.
                break;
        }
        getch();
    } while(choice != 3);
    return 0;
}

Anyone who can teach me how to detect a non-integer input to an integer-type variable using scanf()?

Well... I'd probably say ditch scanf() and use fgets() to read a string, then convert to whatever you want using sprintf(). That may just be me, though. If you're going to experiment with a new form of input, at least experiment with fscanf().

Originally Posted by nowChere

Use scanf to read in a string

*faints*

If I may post my explanation: http://board.theprogrammingsite.com/viewtopic.php?t=223

What a great explanation dwks! That's what I really longing to know--information about %d or %i.. Thank you!