Prefix	Message Category
	ABM	Application desktop toolbar
	BM	Button control
	CB	Combo box control
	CDM	Common dialog box
	DBT	Device
	DL	Drag listbox
	DM	Default push button control
	EM	Edit control
	HDM	Header control
	LB	Listbox control
	LVM	Listview control
	PBM	Progress bar
	PSM	Property sheet
	SB	Status bar window
	SBM	Scrollbar control
	STM	Static control
	TB	Toolbar
	TBM	Trackbar
	TCM	Tab control
	TTM	Tooltip control
	TVM	Tree-view control
	UDM	Up-down control
	WM	General window

Table 1 Message Categories and Prefixes. Symbolic constants used with SendMessage have prefixes that help you understand what they apply to. There are hundreds of messages that use these prefixes. This article uses a subset of the defined EM_ class of messages.