A component of the Microsoft Windows NT executive running in kernel mode that is responsible for message passing. In the Windows NT operating system, applications and their supporting environmental subsystems function in a client/server relationship even though both are located on the same machine.
The Local Procedure Call Facility (LPC Facility) provides the mechanism for client and server components to send messages to each other. The LPC Facility functions in essentially the same way that remote procedure calls (RPCs) do, except with RPCs the client and server components are located on different machines.
When an application on a computer running Windows NT needs to call an application programming interface (API) function on an environmental subsystem such as the Win32 subsystem, the client uses a placeholder called a stub, which is located in a dynamic-link library (DLL).
The stub is used to package and send the parameters being passed to the server subsystem process that implements the call, which unpackages them and executes the called function. The LPC Facility then waits for a response to be issued back. From the application’s point of view, however, the whole process appears to take place locally within the DLL. The application is unaware that the DLL has forwarded the call to another API using the LPC Facility.