Casio PB-1000

The Casio PB-1000 was a handheld computer released by Casio in 1987. It featured a touchscreen display which consisted of 16 keys built into the screen, arranged in fixed positions on a four by four matrix.
The computer itself included 8Kb of RAM and it was possible to install a 32Kb memory expansion card.
The PB-1000 was programmable in both a custom version of the BASIC language and an assembly language. A ROM card could be added for CASL assembly for the educational COMET simulator.