C Programming: Check whether a letter is uppercase or not

Last update on March 20 2025 12:42:38 (UTC/GMT +8 hours)

24. Check Uppercase Letter

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

Sample Solution:

C Code:

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

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

    printf("\n Check whether a letter is uppercase or not :\n");
    printf("------------------------------------------------\n");
    printf(" Input a character : "); // Prompt user to input a character
    scanf("%c", &TestChar); // Read a character from the user

    // Check if the entered character is an uppercase letter
    if (isupper(TestChar)) {
        printf(" The entered letter is an UPPERCASE letter. \n"); // Display message if it is an uppercase letter
    } else {
        printf(" The entered letter is not an UPPERCASE letter. \n"); // Display message if it is not an uppercase letter
    }

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

Output:

 Check whether a letter is uppercase or not :
------------------------------------------------
 Input a character : p
 The entered letter is not an UPPERCASE letter.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to determine if an input character is uppercase by comparing its ASCII value.
• Write a C program to check if a letter is uppercase and then convert it to lowercase if needed.
• Write a C program to verify a character’s case using bitwise operators to test if it is uppercase.
• Write a C program to check whether a character is uppercase and output a corresponding message without library calls.

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