A portable computer arranged to rest comfortably in the hand has a small display screen. Accelerometers capable of detecting movement of the pen with respect to gravity provide input to a microcontroller which selects a response from a number of viewing modes. The pen may be held in either hand and the output message to the screen will be oriented according to the location of the pen. Full personal digital assistance functionality may be incorporated in a relatively small plastics casing and functions, such as calendar, contracts the like may be incorporated.