Preprocessor directive #pragma once

The #pragma once directive has a very simple concept. The header file containing this directive is included only once even if the programmer includes it multiple times during a compilation. This directive works similar to the #include guard idiom. Use of #pragma once saves the program from multiple inclusion optimisation.

// my_header.h
#pragma once
 
void myFunction();

#pragma once

struct Foo {
    int member;
};