Check Whether a Character Is a Vowel, Consonant, Digit, or Special Character in C

This program reads a character from the keyboard and, using if-else statements, determines whether it is a vowel, consonant, digit, or special character.

C Program

#include <stdio.h>

int main() {
    char ch;

    printf("Enter a character: ");
    scanf(" %c", &ch);

    if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
        char lower = (ch >= 'A' && ch <= 'Z') ? ch + 32 : ch;
        if (lower == 'a' || lower == 'e' || lower == 'i' || lower == 'o' || lower == 'u') {
            printf("'%c' is a vowel.\n", ch);
        } else {
            printf("'%c' is a consonant.\n", ch);
        }
    } else if (ch >= '0' && ch <= '9') {
        printf("'%c' is a digit.\n", ch);
    } else {
        printf("'%c' is a special character.\n", ch);
    }

    return 0;
}

Explanation

• The first if checks whether the character falls in the alphabet range (lowercase or uppercase) using ASCII range comparisons.
• Uppercase letters are converted to lowercase by adding 32 (their ASCII offset), so the vowel check only needs to compare against a, e, i, o, u once.
• The next else if checks the ASCII digit range '0' to '9'.
• Anything that's neither a letter nor a digit falls through to "special character" (e.g. punctuation, whitespace, symbols).

Sample Output

Enter a character: e
'e' is a vowel.

Enter a character: k
'k' is a consonant.

Enter a character: 7
'7' is a digit.

Enter a character: #
'#' is a special character.