C Program to Check Whether a Character is a Vowel or Consonant

The five letters A, E, I, O and U are called vowels. All other alphabets except these 5 vowels are called consonants.

This program assumes that the user will always enter an alphabet character.

Program to Check Vowel or consonant :

Program :

#include <stdio.h>
int main() {
    char c;
    int lowercase_vowel, uppercase_vowel;
    printf("Enter an alphabet: ");
    scanf("%c", &c);

    // evaluates to 1 if variable c is a lowercase vowel
    lowercase_vowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');

    // evaluates to 1 if variable c is a uppercase vowel
    uppercase_vowel = (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');

    // evaluates to 1 (true) if c is a vowel
    if (lowercase_vowel || uppercase_vowel)
        printf("%c is a vowel.", c);
    else
        printf("%c is a consonant.", c);
    return 0;
}

Output :

Enter an alphabet: U
U is a vowel.

* The character entered by the user is stored in variable c.

* The lowercase_vowel variable evaluates to 1 (true) if c is a lowercase vowel and 0 (false) for any other characters.

* Similarly, the uppercase_vowel variable evaluates to 1 (true) if c is an uppercase vowel and 0 (false) for any other character.

* If either lowercase_vowel or uppercase_vowel variable is 1 (true), the entered character is a vowel. However, if both lowercase_vowel and uppercase_vowel variables are 0, the entered character is a consonant.

* To fix this, we can use the isalpha() function. The islapha() function checks whether a character is an alphabet or not.

Program :

#include <ctype.h>
#include <stdio.h>

int main() {
   char c;
   int lowercase_vowel, uppercase_vowel;
   printf("Enter an alphabet: ");
   scanf("%c", &c);

   // evaluates to 1 if variable c is a lowercase vowel
   lowercase_vowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');

   // evaluates to 1 if variable c is a uppercase vowel
   uppercase_vowel = (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');

   // Show error message if c is not an alphabet
   if (!isalpha(c))
      printf("Error! Non-alphabetic character.");
   else if (lowercase_vowel || uppercase_vowel)
      printf("%c is a vowel.", c);
   else
      printf("%c is a consonant.", c);

   return 0;
}

Output :

Enter an alphabet: 7
Error! Non-alphabetic character.

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