add "EnableCheats" (without the quotes) at the end
Ingame press "C" to access the ingame cheat menu.
After enabling the in-game cheat menu, press Shift-C at any time during the level to complete the mission with your current stats; using this code at the beginning of a level will net you a Silent Assassin rating.
Press 0 and 1 to activate and deactivate
makes you invisible
Gives you never ending Clips
Gives you unlimited ammo for your guns