You must declare each menu identifier in your application's header file. These constants are used both in the C-language source file and in the resource-definition file.
A menu identifier can be any integer value. The only restriction is that it must be unique within a menu, because no two items in a menu can have the same identifier.
Add the following lines to the header file:
#define IDM_ABOUT 100
/* File-menu items */
#define IDM_NEW 101
#define IDM_OPEN 102
#define IDM_SAVE 103
#define IDM_SAVEAS 104
#define IDM_PRINT 105
#define IDM_EXIT 106
/* Edit-menu items */
#define IDM_UNDO 200
#define IDM_CUT 201
#define IDM_COPY 202
#define IDM_PASTE 203
#define IDM_CLEAR 204