Enter in one of the codes below while playing to activate the desired cheat.

Code - Effect
iddqd - Invincibility 
idkfa - All weapons, keys, ammo, and 200% armor 
idbeholds - Berserker strength 
idbeholdv - Temporary invincibility 
idbeholdi - Temporary invisibility 
idbeholda - Full automap 
idbeholdr - Anti-radiation suit 
idbeholdl - Light amplification visor 
idspispopd - Walk through walls 
idchoppers - Chainsaw 
idclev - Level select 
iddt - Toggle full map; full map and objects; normal map 
idmypos - Display coordinates and heading 
idmus - Change music to indicated level