Nixdorf Computer

A pocket computer made by the German company Nixdorf, the LK-3000 is a curious beast. For starters, its not really a computer at all! What it is... well, its a case containing a display, a keyboard, associated control and decoding circuitry, batteries, a power plug, and a cartridge port... but no processor, no memory, and zero functionality unless a cartridge is inserted.

The cartridge, in turn, may contain a processor, memory, and other components... for instance, even a backup battery to keep continuous CMOS memory powered when the device is turned off or the cartridge is removed.