::TOLOWER

This converts a single character to its lowercase equivalent. The function takes a single argument, typically of type int representing an ASCII character, and returns the corresponding lowercase character if the input is an uppercase letter; otherwise, it returns the character unchanged. ::tolower is often used when performing case-insensitive comparisons, normalizing user input, or processing text to ensure uniformity. For example, converting all characters of a string to lowercase before comparison allows developers to ignore differences in capitalization. It is important to note that ::tolower operates on one character at a time, so when working with strings, it is commonly used in loops or with standard algorithms like std::transform.

#include <algorithm>  // For transform

transform(
    str.begin(),    // Start of the string
    str.end(),      // End of the string
    str.begin(),    // Destination (same string)
    ::tolower       // Function applied to each character (convert to lowercase)
);

#include <iostream>     // For input and output
#include <string>
#include <cctype>
#include <algorithm>    // For transform

using namespace std;

int main() {
    string str = "C++ Programming Is Powerful!";  // Original string
    transform(str.begin(), str.end(), str.begin(), ::tolower);  // Convert to lowercase
    cout << "Lowercase String: " << str << endl;  // Display result
    return 0;  // End of program
}