I want to have two Emacs windows on the screen: one for Dired and one for code. But when I click on a file in the Dired buffer the file opens in the the same window, in place of the Dired buffer. Can I change this behaviour?
Why are you clicking on things with a mouse? I thought you're using Emacs?
Move point to the line you're interested in and press o to open it in another window or C-o to open the file but stay on Dired buffer.
If you must do it with the mouse, use middle-click to do the same thing.