The Diagnostic Test Cartridge is a utility used by technicians to test and troubleshoot the Atari 7800 gaming console's functionality. It wasn't made available for retail sale and was intended strictly for use by authorized service centers. This cartridge runs a series of diagnostics to ensure that the console's hardware components, such as the joystick ports, console switches, and internal circuitry, are working properly. It was released during the Atari 7800's lifespan, which began in 1986.
