DOS

in the GOOD OL' DAYS of computing, a game known as DOOM came out. and in the earliest versions, a screen that says "DOOM Operating System v1.1", and that's nothing more than a screen. It's initials are the same as it's Operating System (MS-DOS) witch stands for Disk Operating System.

Guy 1: Hey, do you remember seeing something that said DOOM Operating System v1.1?
Guy 2: You mean, you saw something that said DOS?
Guy 1: No, boot-up an early version of Doom, and you'll se it.
Guy 2: Oh, alright. Ill do that later.