Hand held video game

A hand held video game unit comprising:

• a controller having a plurality of controller memory locations for the storage of programs and data;
• a video display unit responsive to the operation of the controller for displaying images on the video display unit;
• a first cartridge connection circuit for electrically connecting a cartridge containing computer memory to the controller;
• a second cartridge connection circuit for electrically connecting a second cartridge containing computer memory to the controller;
• apparatus for sensing the connection of a cartridge to the first and second cartridge connectors;
• the controller responds to the sensed presence of a cartridge by controlling the video display unit to display an indication of the connected cartridge;
• and
• said controller transparently changes from one cartridge to another cartridge accessed in a subsequent memory cycle.

In a hand held game unit a method of marking a memory containing cartridge connected to the unit for subsequent access in response to a user selection or a program instruction, comprising the steps of:

• first reading data from a first predetermined memory location of the cartridge;
• first determining the validity of the data in the first predetermined memory location;
• second reading cartridge identity data from a second predetermined memory location of the cartridge;
• decoding the cartridge identity data to determine a plurality of memory location addresses;
• reading security data from the memory locations determined in the decoding step;
• second determining the validity of the security data;
• and
• marking a valid cartridge for subsequent access including via transparent switching.