Header files and #Incldue

Header Files

The header file in C or C++ will have the declarations and definitions that is common for the programming codes. These file usually have the .h or .hpp extensions. In modern days everybody is using the .h extensions for the header files. But, the old days C codes usually have .hpp extension for the header files. However, the C or C++ programming language does not force as to use the .h or .hpp extensions. You can actually use any kind of extensions for the header files. But, to follow the coding standards, it is advisable to use .h

# Include Directive

We call #include as pre-processor directive. Look at the code below:

#include <stdio.h>

 In the above statement, after reading the #include the compiler first replaces the statement with the content of the file. So we have all the definitions and/or declaration required for the file available with us. Note, this is why we do place the #include statements always at the beginning of the file.