3-CppHeaderFiles.cpp

C++ Header Files

Java and CSharp don't have the concept of header files or different types of file.

Header files are used to declare some types of function that can be used in the program who has that include of header file. 

The header files contains only declarations, not deifinitions.

#include  "remo.h"

everything that start with # is a pre-process command or directive so its evaluated before the compilation

#pragma once -> prevents us to include a single header file multiple times into a single transaltion unit. It is because if we declare a STRUCT multile times in a cpp file than we have a duplication error

#ifndef _LOG_H
#define _LOG_H
...
#endif
In this case if _LOG_H is not deined the compiler will go through the #ifndef otherwise it won't. This was used in the past, now we prefer to use #pragma once

Difference between #include "__" and #include <__>
<> the header file is in one of the include directories and does not search for relative paths
"" set a relative path
"../Log.h" go back one directory relative to the directory containing the cpp file and search for Log.h

#include <iostream> it doesn't contain any extention. It has a file with no extentions because c++ separates the C++ standard library header files with the C standard library header files
Header files that are in the standard C library are 
#include<stdlib.h> they have a .h extention
In this way you can differentiate between C and C++ standard library files