How do I change read/write mode for a file using Emacs?

Question

If a file is set to read only mode, how do I change it to write mode and vice versa from within Emacs?

Answer 1

As mentioned up there by somebody else: M-x toggle-read-only would work.

However, this is now deprecated and M-x read-only-mode is the current way to do it, that it is set to C-x C-q keybinding.