Help with 'switch statement' please.

[Andrew Webb]

Hi, I'm writing a program, using switch statements only, and the problem is below:

Write a program, digitsToWords.c, that prompts the user to input a character in the range '0' to'9' (i.e. a digit character). If the user enters '0' the program should print out "ZERO"; if the input is '1' the ouput should be "ONE"; and so on. Any character outside the range '0' to '9' should cause the program to output "NOT A DIGIT". Use a switch statement

i've done most of the program, just need advice on the last part because I can't see what I've done wrong. Any time I enter a non digit, I just get 'zero' printed to the screen and not 'NOT A DIGIT', which I want. Here's what I've written so far:

#include <stdio.h>

int main()
{
    int a;
    
    printf("Please enter a number between 0-9: ");
    scanf("%i", &a);
    
    switch (a) {
        
    case 1 : printf("one\n");
            break;
    case 2 : printf("two\n");
            break;
    case 3 : printf("three\n");
            break;    
    case 4 : printf("four\n");
            break;    
    case 5 : printf("five\n");
            break;
    case 6 : printf("six\n");
            break;    
    case 7 : printf("seven\n");
            break;
    case 8 : printf("eight\n");
            break;    
    case 9 : printf("nine\n");
            break;
    case 0 : printf("zero\n");
            break;
    default: printf("NOT A DIGIT!\n");
            
    }
        return 0;
}

Any help would be great thanks.

[jim mcnamara]

What problem are you having? - the only issues I see:
you do not loop around the switch statement so that the user can enter multiple items (seems to me it is implied from the requirements),
you are supposed to print uppercase ONE ... ZERO.

[Andrew Webb]

Thanks for the reply,

The problem I'm having is if I enter a letter or symbol I will get the message 'zero'. I want it to print 'NOT A DIGIT' and I can't see why it's not doing that.

[vart]

you should check return value of scanf

[Andrew Webb]

ok, so it will treat all characters as integers, so how would I get the program to return 'This is not a digit' when I enter some other than 0-9?

[anduril462]

vart told you, check the return value of scanf. Here, read the scanf documentation for more info. What happens if the user enters "abc" instead of a number?

Also, consider that a is an uninitialized automatic variable. Thus, it's contents are undefined at program startup, and it could have any​ value.

[iMalc]

ok, so it will treat all characters as integers, so how would I get the program to return 'This is not a digit' when I enter some other than 0-9?

It's not that it "treats characters as integers". It's that you've put the result into an integer. That can only always be a number.
So trying to check if it doesn't contain a number is like trying to check if an atom doesn't contain a proton.

Having said that, if you initialise your variable to say -1, then when the scanf fails it should be left alone, and then your switch case should hit the default. The ideal way though is to check return value of scanf.