Expands to the name of the file that is being compiled.
The information is used by the ASSERT and VERIFY macros. The Application Wizard and code wizards place the macro in source code files they create.
#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
// __FILE__ is one of the six predefined ANSI C macros that the
// compiler recognizes.
Reference
ASSERT (MFC)
VERIFY
Concepts
MFC Macros and Globals