C Programming: Check whether a letter is lowercase or not

Last update on March 20 2025 12:42:36 (UTC/GMT +8 hours)

28. Check Lowercase Letter

Write a program in C to check whether a letter is lowercase or not.

Sample Solution:

C Code:

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

int main() {
    char TestChar; // Variable to store the input character

    // Displaying the purpose of the program to the user
    printf("\n Check whether a letter is lowercase or not :\n");  
    printf("------------------------------------------------\n");

    // Prompting user to input a character
    printf(" Input a character : ");
    scanf("%c", &TestChar); // Taking input from user

    // Checking if the entered character is lowercase or not using islower() function
    if (islower(TestChar)) {
        printf(" The entered letter is a lowercase letter. \n"); // Printing the result
    } else {
        printf(" The entered letter is not a lowercase letter. \n"); // Printing the result
    }

    return 0; // Return 0 to indicate successful execution of the program
}

Output:

 Check whether a letter is lowercase or not :
------------------------------------------------
 Input a character : w
 The entered letter is a lowercase letter.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to determine if an input character is lowercase by comparing its ASCII value range.
• Write a C program to check if a letter is lowercase and then convert it to uppercase as part of a toggle function.
• Write a C program to verify a character is lowercase using conditional operators and output an appropriate message.
• Write a C program to validate whether a character is lowercase without resorting to library functions.

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