A command is fully described by its command ID alone (encoded in the WM_COMMAND message). This ID is assigned to the user-interface object that generates the command. Typically, IDs are named for the functionality of the user-interface object they are assigned to.

For example, a Clear All item in the Edit menu might be assigned an ID such as ID_EDIT_CLEAR_ALL. The class library predefines some IDs, particularly for commands that the framework handles itself, such as ID_EDIT_CLEAR_ALL or ID_FILE_OPEN. You will create other command IDs yourself.

When you create your own menus in the Visual C++ menu editor, it is a good idea to follow the class library's naming convention as illustrated by ID_FILE_OPEN. Standard Commands explains the standard commands defined by the class library.

User-Interface Objects and Command IDs