An input system for a computer includes a first input device, such as a mouse or a tablet, and a second input device differing from the first input device. The first input device specifies a position on a display screen, which is connected to a computer for executing an application program and for displaying a processing object area of the application program on the display screen. An instruction set instructs a change in a display state of the processing object area on the display screen in response to an operation of the second input device. The first input device is operated with the operator's favored hand, while the second input device is operated with the operator's non-favored hand. Therefore, both hands are effectively used to improve operation efficiency.