Example: Count Vowels Direct Iteration in C

// Count Vowels Direct Iteration
#include <stdio.h>
#include <string.h> // For strlen()
#include <ctype.h>  // For tolower()

int main() {
    // Step 1: Declare a character array (string) and a counter for vowels.
    char str[100];
    int vowelCount = 0;
    int i; // Loop counter

    // Step 2: Prompt the user to enter a string.
    printf("Enter a string: ");
    
    // Step 3: Read the string from the user.
    // Using fgets to safely read a line of input including spaces.
    // It includes the newline character, so we might need to handle it.
    fgets(str, sizeof(str), stdin);

    // Step 4: Remove the trailing newline character if it exists.
    // strlen(str) returns length including newline if present.
    str[strcspn(str, "\n")] = 0;

    // Step 5: Iterate through the string character by character.
    for (i = 0; str[i] != '\0'; i++) {
        // Step 6: Convert the current character to lowercase for case-insensitive comparison.
        char ch = tolower(str[i]);

        // Step 7: Check if the lowercase character is a vowel.
        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
            vowelCount++;
        }
    }

    // Step 8: Print the total count of vowels.
    printf("Number of vowels in the string: %d\n", vowelCount);

    return 0;
}