To be able to access early unlockables and hidden features in the game escape from the chair at the 'Title' screen and move around to the area behind the chair to find an old computer terminal that you can type one of the following case sensitive codes (without the quotes) to enable the corresponding effect.
Unlock ALL Missions, 'Five' Zombie Mode Mission, Dead Ops Arcade Game, Zork Game:
Enter '3arc Unlock' as a code.
Unlock ALL Intel:
Enter '3arc Intel' as a code.
Display ALL Commands:
Enter 'help' as a code. This displays a list of system commands in the terminal and Pentagon user e-mail access.
Unlock Dead Ops Arcade Game:
Enter 'DOA' as a code. This feature is a zombie killing mini-game similar to Smash TV.
Unlock Zork Game:
Enter 'ZORK' as a code.
Added by: Sanzano Nov 9th 2010, ID#15531