Convert String to Uppercase in C++

transform() function can be used to convert a given string to uppercase.

transform() function can apply a transformation of “to uppercase” for each character in the given string.

In this tutorial, we will learn the syntax and how to use transform() function to convert given string to uppercase, with example programs.

Syntax

The syntax of transform() function to convert a string str to uppercase string is

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

Examples

In the following program, we take a string: str and convert this string to uppercase using transform() function.

C++ Program

#include <iostream>
using namespace std;

int main() {
    string str = "hello world";
    transform(str.begin(), str.end(), str.begin(), ::toupper);
    cout << str << endl;
}

Output

HELLO WORLD
Program ended with exit code: 0

If any of the characters in the given string are already in uppercase, they are left as is.

C++ Program

#include <iostream>
using namespace std;

int main() {
    string str = "Hello World";
    transform(str.begin(), str.end(), str.begin(), ::toupper);
    cout << str << endl;
}

Output

HELLO WORLD
Program ended with exit code: 0

Conclusion

In this C++ Tutorial, we learned how to convert a string to uppercase, with the help of example programs.