"The

The usual use is to write it at the very top of your .h/.cpp files to include other header files like (Windows.h, iostream, cstdio, etc..) to use the what is defined inside in your .h/.cpp file.

The unusual use is to use it to initialize a data-structure like arrays by including a text file that contains the array initialization data between the array initializer list parentheses – e.g XX XXX[] = { <HERE> }. This is is illustrated in the sample program below. The same concept can be used to initialize an array of any dimension.

// main.cpp
#include <cstdio>
#include <Windows.h>

struct Person
{
    char        *pName;
    unsigned    Age;
    unsigned    Height;
    char        Gender;
};

// Declare and initialize a 1D array of Persons structs using PersonTableData text file
// #include "PersonsTableData" will be expanded at COMPILE TIME to the content of PersonsTableData file
Person PersonsTable[] = {
    #include "PersonsTableData"