Count Vowels and Consonants in a String in C

Strings are sequences of characters in C, and manipulating them is a fundamental skill in programming. One common task is to count the number of vowels and consonants present in a string. This helps in text analysis, input validation, and understanding string handling in C.

This tutorial demonstrates how to count vowels and consonants in a string using simple C programs with step-by-step explanation and examples.

Problem Statement

Write a C program to count the number of vowels and consonants in a given string.

Algorithm

Step 1: Start the program.

Step 2: Include `stdio.h` and `ctype.h` for input/output and character functions.

Step 3: Declare a string array to store input and variables to count vowels and consonants.

Step 4: Input the string from the user using `fgets()` for safe input.

Step 5: Traverse each character in the string using a loop.

Step 6: For each character:

- Convert the character to lowercase to simplify comparison.

- If the character is a vowel (a, e, i, o, u), increment the vowel counter.

- Else if the character is an alphabet letter, increment the consonant counter.

Step 7: After the loop ends, print the total number of vowels and consonants.

Step 8: End the program.

C Program to Count Vowels and Consonants

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

int main() {
    char str[200];
    int vowels = 0, consonants = 0;
    int i;

    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);
    if(str[strlen(str)-1] == '\n') str[strlen(str)-1] = '\0';

    for(i = 0; str[i] != '\0'; i++) {
        char ch = tolower(str[i]);
        if(ch >= 'a' && ch <= 'z') {
            if(ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u')
                vowels++;
            else
                consonants++;
        }
    }

    printf("Number of vowels: %d\n", vowels);
    printf("Number of consonants: %d\n", consonants);

    return 0;
}

Example Input/Output

Input:
Enter a string: Hello World

Output:
Number of vowels: 3
Number of consonants: 7

Notes

- The program uses `fgets()` instead of `gets()` for safe input.

- The `tolower()` function converts uppercase letters to lowercase to simplify vowel checking.

- Only alphabetic characters are counted as vowels or consonants; spaces, numbers, and special characters are ignored.

- The program can handle both uppercase and lowercase letters.

Conclusion

Counting vowels and consonants in a string is an excellent way to practice string manipulation and loops in C. This program can be extended to count digits, special characters, or even implement case-insensitive frequency analysis.