Cheat codes are codes that can be entered into a video game to change the game's behaviour. These cheats are usually an exploit of the codes used by the developers to playtest certain aspects of their games; for example, by becoming invulnerable to damage or to skip certain levels of the game. However, many games also include cheat codes intentionally as a form of unlockable reward or Easter egg.
In most cases, codes are activated from within the game itself by pressing a sequence of buttons on the controller. For example, in Die Hard for the Playstation, players could award themselves unlimited ammunition by holding down the R2 button and pressing Right, Up, Down, Down, Square and then Right whilst the game was paused. Cheat codes may also be entered though a PC game console, or they may be enabled by adding special settings in game configuration files (see Cheat Cartridges).
Whilst serious gamers may frown upon cheat codes, they do enable casual players to enjoy a game without having to devote hours of their time to it. Cheat codes may also sometimes be used to bypass serious bugs or glitches that might otherwise freeze the game or cause it to crash.