C Programming: Convert vowels into upper case character in a given string

Last update on August 06 2025 13:02:20 (UTC/GMT +8 hours)

34. Uppercase Vowels in String

Write a C program to convert vowels into uppercase characters in a string.

Sample Solution:

C Code:

#include <stdio.h>

int main() {
    char string1[255]; // Declaring a character array to store the sentence
    int i;

    printf("Input a sentence: ");
    gets(string1); // Input a sentence and store it in string1

    printf("The original string:\n");
    puts(string1); // Print the original sentence

    i = 0;
    // Loop through the string until the end of the string ('\0') is reached
    while (string1[i] != '\0') {
        // Convert lowercase vowels to uppercase by subtracting 32 from their ASCII values
        if (string1[i] == 'a' || string1[i] == 'e' || string1[i] == 'i' || string1[i] == 'o' || string1[i] == 'u') {
            string1[i] = string1[i] - 32;
        }
        i++; // Move to the next character in the string
    }

    printf("After converting vowels into uppercase, the sentence becomes:\n");
    puts(string1); // Print the modified sentence with uppercase vowels
    return 0;
}

Output:

 Input a sentence: The original string:
w3resource
After converting vowels into upper case the sentence becomes:
w3rEsOUrcE

Flowchart:

Flowchart: Convert vowels into upper case character in a given string

For more Practice: Solve these Related Problems:

Write a C program to traverse a string and convert every vowel to its uppercase form.
Write a C program to modify a string so that only the vowels are changed to uppercase while consonants remain unchanged.
Write a C program to convert vowels to uppercase using a switch-case statement for each character.
Write a C program to iterate through a string and replace lowercase vowels with their uppercase counterparts using ASCII manipulation.

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