tolower()

Prototype: int tolower(int chr);
Header File: ctype.h (C) or cctype (C++)
Explanation: Tolower will return the ASCII value for the lowercase equivalent of the ASCII character chr, if it is a letter. If the character is already lowercase, it remains lowercase

//Example reads in a character and makes up lowercase 
#include <iostream>
#include <cctype>

using namespace std;

int main()
{
    char x;
    cin>>x;
    x=tolower(x);
    cout<<x;
}

Other Functions