Interfacing user input devices to a computer

A serial port, input/output controller and central processing unit of a computer 10 co-operate to detect and identify a user input device connected to the serial port and to establish the input device as a master governing functioning of the central processor unit. The input/output controller translates scan code signals from the user input device. The computer may be a mobile client comprising a holster 12 which accommodates a tablet 11 and a cellular telephone for communication with a server 20. The tablet has a liquid crystal display with a touchscreen 15 and an optional keypad (Fig 3). User input may also be via a keyboard 16 or bar code scanner 17 attached to the serial port.