The NES Game Genie from Galoob is a device that allows a player to enter a variety of codes into a Nintendo Entertainment System game in order to cause the game to do things it would not normally do, e.g., grant the player extra (or fewer) lives at startup, give the player extra items, change the gameplay, or just cause crazy things to happen.The NES Game Genie works by allowing the player to plug an NES game cartridge into it and then plug the Game Genie into the NES console in place of the cartridge. The Game Genie then allows the player to enter a code which consists entirely of letters. The codes come in two flavors: 6- and 8- character. The codes translate into addresses and data in a game's program space (upper half of address space, 0x8000-0xFFFF) which the Game Genie fools the CPU into using rather than the byte which is supposed to be there. Because of this method, there is no limit to the number of Game Genie codes that can be discovered.