Check this out here for the basics :
Creating your first MFC Doc/View application[
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#if!defined(AFX_BFICONSULTATIONDOC_H__4D72AF8D_2711_11D4_99F9_0050BA015F99__INCLUDED_)
#define AFX_BFICONSULTATIONDOC_H__4D72AF8D_2711_11D4_99F9_0050BA015F99__INCLUDED_
coming to the above 2 lines : This will help to include the file only one time per compilation process. If this is not there then the same .h will be included multiple times and this may lead to multiple definition errors. You can also use #pragma once instead, but there are few things to note -
#ifndef vs #pragma[
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