Cheat code

A cheat code is a string of characters or commands which unlocks a secret part of a game, not meant to be regularly accessed.

Doom

"iddqd"=Invicibility

"idkfa"=Full keys, armor, and ammo

"idfa"=Full armor, and ammo

"idspisopd"=No clipping

"iddt"=Once, full map, twice, full map with items/enemies, third, back to normal, four times while holding "Alt" in multiplayer, enemies location

"idbehold!"=Gets item where "!" is item, and can be replaced with "I" (Blur Artifact), "R" (Radiation Suit), "S" (Berserk Pack), "A" (Automap), "V" (Invulnerability Artifact) and "L" (Light Amplification Goggles)

"idclev!!"=Warps to level "!!" where "!!" equals "Episode# Mission#"

"idmus!!"=Plays music from level "!!" where "!!" equals "Episode# Mission#"

"idmypos"=Player's coordinates

"idchoppers"=Gets you the Chainsaw

Doom II and Final Doom

"iddqd"=Invicibility

"idkfa"=Full keys, armor, and ammo

"idfa"=Full armor, and ammo

"idclip"=No clipping

"iddt"=Once, full map, twice, full map with items/enemies, third, back to normal, four times while holding "Alt" in multiplayer, enemies location

"idbehold!"=Gets item where "!" is item, and can be replaced with "I" (Blur Artifact), "R" (Radiation Suit), "S" (Berserk Pack), "A" (Automap), "V" (Invulnerability Artifact) and "L" (Light Amplification Goggles)

"idclev!!"=Warps to level "!!" where "!!" is the mission number

"idmus!!"=Plays music from level "!!" where "!!" is the mission number

"idmypos"=Player's coordinates

"idchoppers"=Gets you the Chainsaw

Doom 95

"fhhall"=Kills all monsters on level

"fhshh"=Monsters don't notice you unless you shoot somewhere in the room, or at them. Doors don't cause them to notice you, either.