The Commodore is a home computer from the 1980s.

The +4 has a number of interfaces which can be used to connect to the outside world. These include a serial UART, 8-bit parallel port, cassette port and a CBM IEC serial bus.

 1   2   3   4   5   6   7   8   9   10  11  12
GND 5V  RES P2  P3  P4  P5  RxC ATN  9V  9V GND

GND P0  RxD RTS DTR P7  DCD P6  P1  DSR TxD GND
 A   B   C   D   E   F   H   J   K   L   M   N