The computer was primarily sold as a kit; two Eurocard boards (160mm x 100mm) had first to be populated and wired together. These form a self-contained and unusually compact computer, needing only a 9-volt power supply. The visible (top) board is the Acorn Keyboard:
In addition to the white keyboard, this board also holds a 9-digit calculator-style 7-segment LED display (of which only 8 digits can be used) and, on the left, circuitry for the cassette recorder interface (and a scan decoder).
of the first 128 bytes of the Acorn Monitor program, as would be recorded on a cassette tape (your browser may need a plug-in to play this MIDI file).
In this picture the display is showing the contents of the memory location at address (A.) FE00, namely A0. This is the first byte of the firmware monitor program.
On the keyboard, the sixteen keys on the left provide for hexadecimal input values. The eight keys to their right initiate the following command functions:
| m | (modify) Memory display and modification | l | (load) Reads a block of bytes from tape |
| g | (go) Run program starting at an address | r | (return) Resume after a breakpoint |
| p | (point) Inserts or removes breakpoint | ^ | (up) Increment displayed address |
| s | (store) Writes a block of bytes to tape | v | (down) Decrement displayed address |
The rst key resets the microprocessor, which starts the monitor program (which in turn initially displays eight dots, then waits for a command key to be pressed).
