C Program to Check Vowel or Consonant

Use a C program that reads a character and checks if it is a vowel by comparing it with 'a', 'e', 'i', 'o', 'u' (both lowercase and uppercase), else it is a consonant; for example, if(ch=='a'||ch=='e'||ch=='i'||ch=='o'||ch=='u'||ch=='A'||ch=='E'||ch=='I'||ch=='O'||ch=='U').

Examples

Inputa

Outputa is a vowel

InputB

OutputB is a consonant

Inputz

Outputz is a consonant

How to Think About It

To check if a character is a vowel or consonant, first get the character input. Then compare it with all vowels in lowercase and uppercase using or conditions. If it matches any vowel, print it is a vowel; otherwise, print it is a consonant.

Algorithm

1

Get a character input from the user

2

Check if the character is one of 'a', 'e', 'i', 'o', 'u' or their uppercase versions

3

If yes, print that the character is a vowel

4

Otherwise, print that the character is a consonant

Code

c

#include <stdio.h>
int main() {
    char ch;
    printf("Enter a character: ");
    scanf(" %c", &ch);
    if(ch=='a'||ch=='e'||ch=='i'||ch=='o'||ch=='u'||
       ch=='A'||ch=='E'||ch=='I'||ch=='O'||ch=='U') {
        printf("%c is a vowel\n", ch);
    } else {
        printf("%c is a consonant\n", ch);
    }
    return 0;
}

Output

Enter a character: a
a is a vowel

Dry Run

Let's trace the input 'a' through the code

1

Input character

User inputs 'a'

2

Check vowel condition

Check if 'a' equals any vowel (a, e, i, o, u or uppercase)

3

Condition true

'a' matches 'a', so condition is true

4

Print result

Print 'a is a vowel'

Step	Character	Condition (is vowel?)	Output
1	a	true	a is a vowel

Why This Works

Step 1: Input character

The program reads a single character from the user using scanf.

Step 2: Check vowels

It compares the character with all vowels in lowercase and uppercase using or conditions.

Step 3: Print result

If the character matches any vowel, it prints it is a vowel; otherwise, it prints it is a consonant.

Alternative Approaches

Using switch-case

c

#include <stdio.h>
int main() {
    char ch;
    printf("Enter a character: ");
    scanf(" %c", &ch);
    switch(ch) {
        case 'a': case 'e': case 'i': case 'o': case 'u':
        case 'A': case 'E': case 'I': case 'O': case 'U':
            printf("%c is a vowel\n", ch);
            break;
        default:
            printf("%c is a consonant\n", ch);
    }
    return 0;
}

Switch-case improves readability by grouping vowel cases together.

Using a function to check vowels

c

#include <stdio.h>
#include <ctype.h>
int isVowel(char ch) {
    ch = tolower(ch);
    return ch=='a'||ch=='e'||ch=='i'||ch=='o'||ch=='u';
}
int main() {
    char ch;
    printf("Enter a character: ");
    scanf(" %c", &ch);
    if(isVowel(ch))
        printf("%c is a vowel\n", ch);
    else
        printf("%c is a consonant\n", ch);
    return 0;
}

Using a function and <code>tolower</code> reduces repeated code and handles case uniformly.

Complexity: O(1) time, O(1) space

Time Complexity

The program performs a fixed number of comparisons regardless of input size, so it runs in constant time O(1).

Space Complexity

It uses only a few variables and no extra data structures, so space complexity is O(1).

Which Approach is Fastest?

All approaches run in constant time; using tolower() with a function improves readability without affecting speed.

Approach	Time	Space	Best For
If-else conditions	O(1)	O(1)	Simple and direct checks
Switch-case	O(1)	O(1)	Better readability with grouped cases
Function with tolower()	O(1)	O(1)	Cleaner code and case handling