toupper c++

                                    char choice; 
// it will instantly transform it to upper case without the need
// to convert it to int first
choice = (char)toupper(choice);

                                    transform(str.begin(), str.end(), str.begin(), ::toupper); 

                                    #include <cctype>
#include <iostream>
#include <cstring>
#include <cstdio>

using namespace std;

int main()
{
    char str[] = "John is from USA.";

    cout << "The uppercase version of \"" << str << "\" is " << endl;

    for (int i=0; i<strlen(str); i++)
        putchar(toupper(str[i]));
    
    return 0;
}

                                    int result = toupper(charecterVariable);// return the int that corresponding upper case char
//if there is none then it will return the int for the original input.
//can convert int to char after
char result2 = (char)toupper(variableChar);

                                    // toupper example (C++)
#include <iostream>       // std::cout
#include <string>         // std::string
#include <locale>         // std::locale, std::toupper

int main ()
{
  std::locale loc;
  std::string str="Test String.\n";
  for (std::string::size_type i=0; i<str.length(); ++i)
    std::cout << std::toupper(str[i],loc);
  return 0;
}

/*
Output:
TEST STRING.
*/