The up and down arrow keys cycle through the commands you've entered and the right arrow automatically enters, character by character, the last command you executed.This might not sound that interesting, but there are several situations where the arrow keys become huge time savers.
Consider this example: You've typed out 75 characters of a command and then try to execute it, only to find that you forgot to add an option at the very end. No problem, just press the up arrow and the entire command is automatically entered in the Command Prompt window, ready for you to edit to make it work.