Abstract: A companion computer system for a host computer wherein the host computer includes an interface for electrically and mechanically interfacing to the companion computer. An example is a PCMCIA slot. The companion system includes a PC card with an interface which mates with the interface on the host. A bus is located on the PC card. A CPU is located on the PC card and connected to the bus. A display is located on the PC card and connected to the bus. An input device is located on the PC card and connected to the bus. A non-volatile memory module is located on the PC card and connected to the bus. A low power random access memory module is located on the PC card and connected to the bus. A power supply is located on the PC card and connected to the components of the PC card An operating system is located in the non-volatile memory.

Abstract: A modular PCMCIA card comprises a base member conforming to the Type I or Type II physical dimensions and an add on section which mechanically and electrically connects with the base member and has dimensions such that when the base member and the add on section are joined, they conform to the dimensions of a PCMCIA Type III card. The add on section may contain one or more functional units of a stand alone computer system and may also contain a battery, a modem, pager and/or an infrared transceiver for communicating with printers, computers or controlling other devices.