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.