Headers in C++ - Cyborg Coding

In C++, headers are a way to separate the interface of a class or function from its implementation. A header file, typically with the file extension ".h" or ".hpp", contains the declarations of a class or function, including its name, data members, and member functions. The implementation of the class or function, including the actual code for the member functions, is typically stored in a separate source file, typically with the file extension ".cpp".

When a header file is included in a source file, the compiler uses the declarations in the header file to verify that the corresponding class or function is used correctly in the source file. The actual code for the class or function is not included in the source file until it is linked with the object file generated from the corresponding source file during the compilation process.

Headers also allow for code reuse, as a class or function that is defined in a header file can be used in multiple source files, without having to rewrite the same code in each source file.

The #include directive is used to include a header file in a source file. The #include directive tells the preprocessor to substitute the contents of the specified header file in place of the #include statement.

For example:

#include <iostream>

This will include the header file <iostream> which contains the declarations for the standard input/output library in C++.

It's also possible to include header files that you created, by specifying the path to the header file. For example:

#include "MyHeader.h"

This will include the header file "MyHeader.h" which contains the declarations for the class or function you created.

It's also a good practice to use guards in the header files. A guard is a preprocessor directive that prevents a header file from being included more than once in a single source file. This is important because if a header file is included more than once, it can cause compilation errors or unexpected behavior.

In summary, headers in C++ are a way to separate the interface of a class or function from its implementation. A header file contains the declarations of a class or function, including its name, data members, and member functions. The actual code for the class or function is stored in a separate source file. Headers allow for code reuse and are included in source files using the #include directive. It's also a good practice to use guards in the header files to prevent errors caused by including a header file multiple times.