On the Main Menu, alternately tap RIGHT and LEFT triggers. After about 5 taps a piece, you'll stand up. Leave your seat and examine the back wall. A small black and white computer terminal can be found here. Approach it and enter these codes using the on-screen keyboard in the "Central Intelligence Agency Data System."
DOA - Play the super-awesome top-down Smash TV-style Dead Ops Arcade minigame
3ARC INTEL - Unlocks all the intel in the game for viewing (Disables Closer Analysis Trophy/Achievement)
3ARC UNLOCK - Unlocks all Zombie Mode levels
ZORK - Unlocks Zork I: The Great Underground Empire (an incredibly great text adventure from 1980) which you can play on the console (!)
HELP - Gives you a list of commands to interface with the console -- you can check mail messages and perform other mundane functions, some of which are listed below
DIR - Gives a list of audio files and pictures which you can open with the CAT command (e.g. CAT NoteX.txt)
WHO - Gives a list of login names for use with the RLOGIN function (but they require a password)
Source= Call of Duty: Black Ops Cheats - PS3 Cheats & Codes - PlayStation 3 - IGN
