Input Devices

Light Pen
Light pens are electronic pointers that allow users to modify designs on-screen. The hand-held pointer contains sensors that send signals to the computer whenever light is recorded. The computer’s screen is not lit up all at once, but traced row-by-row by an electron beam sixty times every second. Because of this, the computer is able to determine the pen’s position by noting exactly when the pen detects the electron beam passing its tip. Light pens are often used in computer-aided design and computer-aided manufacture (CAD and CAM) technology because of the flexibility they provide. Here, an engineer uses a light pen to modify a technical drawing on a computer display screen.

Input devices, such as a keyboard or mouse, permit the computer user to communicate with the computer. Other input devices include a joystick, a rodlike device often used by people who play computer games; a scanner, which converts images such as photographs into digital images that the computer can manipulate; a touch panel, which senses the placement of a user’s finger and can be used to execute commands or access files; and a microphone, used to input sounds such as the human voice which can activate computer commands in conjunction with voice recognition software. “Tablet” computers are being developed that will allow users to interact with their screens using a penlike device.