(C programming) while true loop with switch case, always run in default case

Question

I am a newbie to C programming. I'm practicing to read the user input through an infinite while loop, and check if the input is a vowel or constant. I use a switch to check it, however when I execute my code, the default case is always executed, and I got stucked.

Would be appreciate if anyone can give me some advice, thanks!

#include <stdio.h>

void checkIfVowel(char *c);

int main()
{
    char c;
    while (1)
    {
        printf("Please enter a character: ");
        scanf("%c", &c);
        checkIfVowel(&c);
    }
    return 0;
}

void checkIfVowel(char *c)
{
    switch (*c)
    {

    case 'A':
        printf("%c is a vowel! \n", *c);
        break;
    case 'E':
        printf("%c is a vowel! \n", *c);
        break;
    case 'I':
        printf("%c is a vowel! \n", *c);
        break;
    case 'O':
        printf("%c is a vowel! \n", *c);
        break;
    case 'U':
        printf("%c is a vowel! \n", *c);
        break;
    case 'a':
        printf("%c is a vowel! \n", *c);
        break;
    case 'e':
        printf("%c is a vowel! \n", *c);
        break;
    case 'i':
        printf("%c is a vowel! \n", *c);
        break;
    case 'o':
        printf("%c is a vowel! \n", *c);
        break;
    case 'u':
        printf("%c is a vowel! \n", *c);
        break;
    default:
        printf("%c is a constant! \n", *c);
        break;
    }
}

Newline is a character too and will be returned by `scanf("%c",..)`. — interjay, Jul 24 '21 at 09:01
What if you replace the `scanf()` call and hard-code some values. Does it work then? In that case, your use of `scanf()` is what causes the problems. — Ulrich Eckhardt, Jul 24 '21 at 09:03
See this answer: https://stackoverflow.com/questions/13542055/how-to-do-scanf-for-single-char-in-c — Daniel Kleinstein, Jul 24 '21 at 09:03
You don't need to pass a pointer to `checkIfVowel`. And you don't need all those `printf` calls in the function... `case 'A': case 'E': ... case 'U': printf(...); break;` will work as well. — Some programmer dude, Jul 24 '21 at 09:04
I also recommend you learn about [`toupper`](https://en.cppreference.com/w/c/string/byte/toupper) and [`tolower`](https://en.cppreference.com/w/c/string/byte/tolower). Half of your cases could be omitted. — Some programmer dude, Jul 24 '21 at 09:06
Just tried the code in [OnlineGDB](https://www.onlinegdb.com/) and it worked. I don't see any problems here excluding code quality. — BlueStaggo, Jul 24 '21 at 09:42
Brandon TW, To simplify `checkIfVowel()`, research `strchr()`. — chux - Reinstate Monica, Jul 24 '21 at 10:33

score 0 · Answer 1 · answered Jul 24 '21 at 10:46

Simple change is enough to remove errors. But you can simply do this even with if- else statement with logical conditions for all the vowel within 1 line of code rather than this switch cases.! just try it! I'm attaching error removed code only

#include <stdio.h>

void checkIfVowel(char *c);

int main()
{
    char c;
    while (1)
    {
        printf("Please enter a character: ");
        scanf("%c", &c);
        checkIfVowel(c);
    }
    return 0;
}

void checkIfVowel(char* c)
{
    switch ((char) c)
    {

    case 'A':
        printf("%c is a vowel! \n", c);
        break;
    }
    
}

(C programming) while true loop with switch case, always run in default case

1 Answers1