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C++ program to convert lowercase character to uppercase and vice versa

Given a lowercase/uppercase character, we have to convert it into uppercase/lowercase using C++ program.
[Last updated : February 27, 2023]

Problem statement

In this program, we will learn how to convert an entered character from lowercase to uppercase and uppercase to lowercase in C++?

Converting lowercase character to uppercase and vice versa

Here, we will read a character and check whether it is a valid alphabet or not, if it is a valid alphabet (from A-Z or a-z), we will check uppercase character, if it is uppercase character - we will convert it into lowercase character and if it is in Lowercase character - we will convert it into uppercase character.

To convert uppercase to lowercase - we are adding 32 in the ASCII value of uppercase character because the difference between Uppercase and Lowercase characters are 32. Same to convert lowercase character to uppercase - we are subtracting 32 in the ASCII value of lowercase character.

C++ program to convert lowercase character to uppercase and vice versa

#include <iostream>
using namespace std;

int main()
{
    char ch;

    cout << "Please input a valid character (Alphabet): ";
    cin >> ch;

    //check for valid alphabet
    if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z')) {
        //check case and convert into opposite case
        if (ch >= 'A' && ch <= 'Z')
            ch = ch + 32;
        else if (ch >= 'a' && ch <= 'z')
            ch = ch - 32;
        else
            ; //none

        cout << "converted character is: " << ch << endl;
    }
    else {
        cout << "Entered character is not a valid alphabet!!!" << endl;
    }

    return 0;
}

Output

First run:
Please input a valid character (Alphabet): H
converted character is: h

Second run:
Please input a valid character (Alphabet): h
converted character is: H

Third run:
Please input a valid character (Alphabet): &
Entered character is not a valid alphabet!!!