C program to check whether a character is Uppercase or Lowercase

Write a C program to input character from user and check whether character is uppercase or lowercase alphabet using if else. How to check uppercase and lowercase using if else in C programming. Logic to check uppercase and lowercase alphabets in C program.

Example
Input

Input character: C

Output

'C' is uppercase alphabet

Required knowledge

Basic C programming, Relational operators, Logical operators, If else

Logic to check uppercase and lowercase alphabets

Step by step descriptive logic to check uppercase and lowercase alphabets.

  1. Input a character from user. Store it in some variable say ch.
  2. Character is uppercase alphabet if(ch >= 'A' and ch <= 'Z').
  3. Character is lowercase alphabet if(ch >= 'a' and ch <= 'z').
  4. If none of the above conditions met, then character is not alphabet.

Program to check uppercase or lowercase alphabets

/**
 * C program to check whether a character is uppercase or lowercase 
 */

#include <stdio.h>

int main()
{
    char ch;

    /* Input character from user */
    printf("Enter any character: ");
    scanf("%c", &ch);


    if(ch >= 'A' && ch <= 'Z')
    {
        printf("'%c' is uppercase alphabet.", ch);
    }
    else if(ch >= 'a' && ch <= 'z')
    {
        printf("'%c' is lowercase alphabet.", ch);
    }
    else
    {
        printf("'%c' is not an alphabet.", ch);
    }

    return 0;
}

You can also use inbuilt library function isupper() and islower() to check uppercase and lowercase alphabets respectively. These functions are present in ctype.h header file. Both function returns 1 if given character is uppercase or lowercase respectively otherwise returns 0.

Program to check uppercase or lowercase characters using library functions

/**
 * C program to check whether a character is uppercase 
 * or lowercase using inbuilt library functions
 */

#include <stdio.h>
#include <ctype.h> /* Used for isupper() and islower() */

int main()
{
    char ch;

    /* Input character from user */
    printf("Enter any character: ");
    scanf("%c", &ch);

    if(isupper(ch))
    {
        printf("'%c' is uppercase alphabet.", ch);
    }
    else if(islower(ch))
    {
        printf("'%c' is lowercase alphabet.", ch);
    }
    else
    {
        printf("'%c' is not an alphabet.", ch);
    }

    return 0;
}

The statement if(isupper(ch)) is equivalent to if(isupper(ch) == 1).

Output

Enter any character: C
'C' is uppercase alphabet.

Happy coding 😉

About Pankaj

Pankaj Prakash is the founder, editor and blogger at Codeforwin. He loves to learn new techs and write programming articles especially for beginners. He works at Vasudhaika Software Sols. as a Software Design Engineer and manages Codeforwin. In short Pankaj is Web developer, Blogger, Learner, Tech and Music lover.

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