Here is the code:

#define APP_NAME "COM Example (ch 5)"
#define WIDTH 100
#define HEIGHT 100

#include 
#include 

typedef IUnknown* (*CREATEFUNCPTR)() ;

IUknown* CallCreateInstance( HWND hWnd, char* name )
{
	HINSTANCE hComponent = ::LoadLibrary( name );

	if( hComponent == NULL )
	{
		MessageBox( hWnd, "INVALID FILE NAME", "ERROR", MB_OK );
		return NULL;
	}

	CREATEFUNCPTR CreateInstance = (CREATEFUNCPTR)::GetProcAddress( hComponent, "CreateInstance" );

	if( CreateInstance == NULL )
	{
		MessageBox( hWnd, "COULD NOT LOCATE CreateInstance", "ERROR", MB_OK );
		return NULL;
	}

	return CreateInstance();
}

LRESULT CALLBACK WndProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
	switch( msg )
	{
	case WM_DESTROY:
		PostQuitMessage( 0 );
		return 0;

	default:
		return DefWindowProc( hWnd, msg, wParam, lParam );
	}
}

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE, LPSTR, int )
{
	HWND hWnd;
	MSG	msg;
	WNDCLASS wc;

	wc.cbClsExtra		= NULL;
	wc.cbWndExtra		= NULL;
	wc.hbrBackground	= (HBRUSH)GetStockObject( GRAY_BRUSH );
	wc.hCursor			= LoadCursor( NULL, IDC_ARROW );
	wc.hIcon			= LoadIcon( NULL, IDI_APPLICATION );
	wc.hInstance		= hInstance;
	wc.lpfnWndProc		= WndProc;
	wc.lpszClassName	= APP_NAME;
	wc.lpszMenuName		= NULL;
	wc.style			= CS_HREDRAW / CS_VREDRAW;

	RegisterClass( &wc );

	hWnd = CreateWindow( APP_NAME, APP_NAME, WS_OVERLAPPEDWINDOW, 0, 0, WIDTH, HEIGHT, NULL, NULL, hInstance, NULL );

	ShowWindow( hWnd, SW_SHOW );
	UpdateWindow( hWnd );

	while( GetMessage( &msg, 0, 0, 0 ) == TRUE )
	{
		TranslateMessage( &msg );
		DispatchMessage( &msg );
	}

	return msg.wParam;
}
 

Here is the problem:

Compiling...
win_main.cpp
C:\Programming\C++\COM_ch5\win_main.cpp(10) : error C2143: syntax error : missing '';'' before ''*''
C:\Programming\C++\COM_ch5\win_main.cpp(10) : error C2501: ''IUknown'' : missing storage-class or type specifiers
C:\Programming\C++\COM_ch5\win_main.cpp(11) : error C2501: ''CallCreateInstance'' : missing storage-class or type specifiers
C:\Programming\C++\COM_ch5\win_main.cpp(28) : error C2440: ''return'' : cannot convert from ''struct IUnknown *'' to ''int''
        This conversion requires a reinterpret_cast, a C-style cast or function-style cast
Error executing cl.exe.

win_main.obj - 4 error(s), 0 warning(s)
 

I believe errors basically say that IUnKnown is undifined; why? Help.

> C:\Programming\C++\COM_ch5\win_main.cpp(10) : error
> C2143: syntax error : missing '';'' before ''*''

That would be this line..

IUknown* CallCreateInstance( HWND hWnd, char* name )

IUnknown* not IUknown* ... and that should make it work.

oops...