What is the difference between closing an application and ending the process from Task Manager?

Question

What is the difference between killing an application using the close button and ending the process from the Task Manager?

I am aware of the fact that hitting the cl

Answer 1

Killing the process with WM_CLOSE simply signals the process with the message and allows the target to handle the message and exit gracefully. Alternatively, the process could choose not to exit in its WM_CLOSE handler.

Killing the process via task manager will do so with TerminateProcess which is far harsher:

The TerminateProcess function is used to unconditionally cause a process to exit. The state of global data maintained by dynamic-link libraries (DLLs) may be compromised if TerminateProcess is used rather than ExitProcess.

This function stops execution of all threads within the process and requests cancellation of all pending I/O. The terminated process cannot exit until all pending I/O has been completed or canceled. When a process terminates, its kernel object is not destroyed until all processes that have open handles to the process have released those handles.

TerminateProcess is asynchronous; it initiates termination and returns immediately. If you need to be sure the process has terminated, call the WaitForSingleObject function with a handle to the process. A process cannot prevent itself from being terminated.