Application-Defined Messages

An application can create messages to be used by its own windows or to communicate with windows in other processes. If an application creates its own messages, the window procedure that receives them must interpret the messages and provide appropriate processing.

Windows reserves message-identifier values in the range 0x0000 through 0x03FF (the value of WM_USER 1) and 0x8000 through 0xBFFF for system-defined messages. Applications cannot use these values for private messages.

Values in the range 0x0400 (the value of WM_USER) through 0x7FFF are available for message identifiers defined by an application for its own use. Values in the range 0xC000 through 0xFFFF are available for message identifiers defined by an application for use in communicating with windows in other applications.

Windows returns a message identifier in the range 0xC000 through 0xFFFF when an application calls the RegisterWindowMessage function to register a message. The message identifier returned by this function is guaranteed to be unique throughout the system. Use of this function prevents conflicts that can arise if other applications use the same message identifier for different purposes.

Software for developers

Delphi Components
.Net Components
Software for Android Developers

More information resources

MegaDetailed.Net
Unix Manual Pages
Delphi Examples

Databases for Amazon shops developers

Amazon Categories Database
Browse Nodes Database