DOCERR: Overview Manual Documents PostAppMessage Incorrectly

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SUMMARY

Section 1.1.4 (page 10) of the "Microsoft Windows Software Development Kit: Programmer's Reference, Volume 1: Overview" manual for version 3.1 documents that the PostAppMessage function posts a message to an application using its module handle. This statement is incorrect; PostAppMessage posts a message to an application using its task handle.

MORE INFORMATION

Microsoft Windows makes a very important distinction between a task handle and a module handle. Each instance of an application has exactly one task, which consists of a stack, a message queue, and an execution state (CPU registers). However, all instances of an application share the same module, which consists of the application's executable code and resources.

One cannot post a message to a module for two reasons:

• A module does not have a message queue; therefore, it cannot process a message.
• Potentially, several application instances (tasks) share a module; therefore, a module handle does not identify a unique task to receive the message.