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tolower() Function in C++

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The C++ tolower() function converts an uppercase alphabet to a lowercase alphabet. It is a predefined function of ctype.h header file. If the character passed is an uppercase alphabet, then the tolower() function converts an uppercase alphabet to a lowercase alphabet. This function does not affect another lowercase character, special symbol, or digit.

int tolower(int ch);

Parameter:

  • ch: It is the character to be converted to lowercase.

Return Value: This function returns the ASCII value of the lowercase character corresponding to the ch.

In C++, typecasting of int to char is done as follows:

char c = (char) tolower('A');

Below programs illustrate the tolower() function in C++:

Example 1:

C++




// C++ program to demonstrate
// example of tolower() function.
  
#include <iostream>
using namespace std;
  
int main()
{
  
    char c = 'G';
  
    cout << c << " in lowercase is represented as = ";
  
    // tolower() returns an int value there for typecasting
    // with char is required
    cout << (char)tolower(c);
}


Output

G in lowercase is represented as = g

Example 2:

C++




// C++ program to convert a string to lowercase
// using tolower
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    // string to be converted to lowercase
    string s = "GEEKSFORGEEKS";
    
    for (auto& x : s) {
        x = tolower(x);
    }
    
    cout << s;
    return 0;
}


Output

geeksforgeeks

Note:  If the character passed in the tolower() is any of these three

  1. lowercase character
  2. special symbol
  3. digit

tolower() will return the character as it is.

Example 3:

C++




// C++ program to demonstrate
// example of tolower() function.
#include <iostream>
using namespace std;
  
int main() {
  
    string s="Geeks@123";
    
      for(auto x:s){
        
          cout << (char)tolower(x);
    }
    
    return 0;
}


Output

geeks@123

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Last Updated : 11 Mar, 2023
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