Question

I wonder whether #include also means “use”. If not, would you please tell me what the compiler will do with the extra files, included functions? If yes, does this mean they have their memories allocated in the output PE?

Answer 1

#include "file.h" tells the preprocessor to open file.h and merge the content of this file with the current file in which you write #include "file.h".

That is, if you have two files as:

//file.h
extern int x;

//file.cpp
#include "file.h"

int x;
void f()
{
    x = 10;
}

Then preprocessor copies the content of file.h to file.cpp as:

extern int x; //came from file.h

int x;
void f()
{
    x = 10;
}