is a latching type, the shift-lock key. When supplied as a kit, the keyboard was assembled by the purchaser from a bag of switches and keytops. The keyboard ports are located at address DF00 (hex), or 57088 (decimal). BASIC programs typically poll for real-time keyboard input by using the PEEK and POKE commands at that address. Because the keyboard lacks any way to generate an interrupt, it is not possible to implement a typeahead buffer. The keyboard matrix also lacks any diodes at the intersections of the matrix. This leads to problems when reading certain combinations of keys pressed simultaneously. The matrix was designed to allow only the shift, control and shift-lock keys to be pressed simultaneously with another key. The keyswitches themselves were originally manufactured by Cherry. Program Storage In common with other home computers of the time, software can be saved and loaded on standard cassette tapes. The UK101 uses the Kansas City standard tape format. I/O is managed by a Motorola 6850 ACIA. This allows a full RS-232 port to be implemented, with the addition of a few extra components and minor modifications to existing jumpers on the board. Compared to the Superboard Although very similar to the Ohio Scientific Superboard II, the Compukit UK101 differed from that machine in a few places: Video display of the UK101 works at UK frequency and resolution. RF output is UHF, to suit domestic TVs in the UK. Power supply is located on the main PCB and accepts UK 240 V AC mains input (via a transformer). Display improved to 48 characters per line Memory increased to 8 KB However, similarities in the PCB layout make it clear that this machine is a clone. The people involved with the modifications were Chris Cary and Bill Wood. Expansion The 40 pin expansion socket opened up the world to the UK101. One could attach a dual floppy disk controller (5.25") and a memory expansion card (40K max) to allow faster and reliable save/load of programs/data. A sound card became available, built around the General Instrument AY-3-8910, which together with a Peripheral Interface Adapter (PIA) WDC 65C21 chip, gave the UK101 audio abilities. The UK101 floppy disk interface utilised a PIA to control the floppy disk drive stepper motor and another ACIA to serialise the data written to the disk. A disk operating system was used to provide file storage capability but this