second generation
The earliest console, the Magnavox Odyssey, had used removeable cartridges that were nothing but glorified jumpers to activate the games already wired in to the console. This method was soon replaced during the move to PONG consoles, where the logic for one or more games was hardcoded into microchips using discrete logic, and no additional games could ever be added. By the mid-1970's cartridges had returned with the move to CPU based consoles. With games now consisting of microprocessor based code, these games were burned onto ROM chips that were mounted inside plastic cartridge casings that could be plugged into slots on the console. When the cartridges were plugged in, the general-purpose microprocessors in the consoles read the cartridge memory and ran whatever program was stored there. Rather than being confined to a small selection of games included in the box, consumers could now amass libraries of game cartridges