#include Directive

#include directive physically includes the contents of a specified file into the current file.

Syntax:

#include "filename"

or

#incude <filename>

When used in its first form, the referenced file is searched in the same folder as the current file. When used in the second form, a file is searched in a list of standard include folders, which you can manage on Structure Viewer Settings Page.

For example, let us have following two files:

File1.h:

struct A
{
    // …
};
      

And File2.h:

#include "File1.h"

struct B
{
    A a;
};
      

If there was no #include directive in File2.h, you would not be able to add this file to a Structure Library, as it uses an undefined type A. But preprocessor, which runs on the file before it is compiled, transforms the file into the following:

struct A
{
    // …
};

struct B
{
    A a;
};
      

That is, it physically inserts the contents of File1.h into File2.h, thus, making File2.h compilable. See also the #pragma once directive.

Using Absolute and Relative Paths

Both syntax forms, form 1 and form 2 allow you to specify absolute or relative paths, for example:

#include "c:\Projects\definitions.h"     // will use an absolute path
#include "..\inc\definitions.h"          // includes "definitions.h" file, located in "inc" sibling
#include <lib\definitions.h>             // includes "definitions.h" file, located in "lib" subdirectory 
                                         // of one of standard include paths.