Handle object in c++

Question

I've been told that a handle is a sort of "void" pointer. But what exactly does "void pointer" mean and what is its purpose. Also, what does "somehandle = GetStdHandle(STD_INPUT_HANDLE); do?

Answer 1

A handle in the general sense is an opaque value that uniquely identifies an object. In this context, "opaque" means that the entity distributing the handle (e.g. the window manager) knows how handles map to objects but the entities which use the handle (e.g. your code) do not.

This is done so that they cannot get at the real object unless the provider is involved, which allows the provider to be sure that noone is messing with the objects it owns behind its back.

Since it's very practical, handles have traditionally been integer types or void* because using primitives is much easier in C than anything else. In particular, a lot of functions in the Win32 API accept or return handles (which are #defined with various names: HANDLE, HKEY, many others). All of these types map to void*.

Update:

To answer the second question (although it might be better asked and answered on its own):

GetStdHandle(STD_INPUT_HANDLE) returns a handle to the standard input device. You can use this handle to read from your process's standard input.