Computer Peripheral Devices

What is a computer peripheral device then? Any device connected internally or externally to a computer and used in the transfer of data is called a peripheral device. Entering and displaying information is carried out on a wide variety of peripherals, which are also known as input output (I/O) devices.

Some peripherals, such as keyboards, are only input devices; other peripherals, such as printers, are only output devices; and some are both. Peripherals may be inside or outside the computer’s container. The I/O bus is the collection of circuits where an inside devise is attached. An I/O port is a connector where an outside device is plugged in.

Input devices send information and instructions to the computer. Some input devices are hand operated, but others work automatically once they are turned on. There are main kinds of hand-operated units: a keyboard, a mouse, a trackball, a touchpad, a digitizing tablet, a touch screen, a light pen, and a joystick. There are three types of automatic units: a modem, a scanner and a microphone. In addition, all storage devices can function as input devices.

A keyboard is the main input device of most computers. Modern computer keyboards have letter and numeral keys organized in the same way as typewriter keyboards. A cordless keyboard uses infrared radio waves instead of a cable to send information to the computer. It enables a user to work at a greater distance from the screen that a cable will allow.

A mouse is a palm-sized device that the computer user moves about on a flat surface. An optical mouse does not use a ball but instead uses small light sources and detectors to determine the movement of the mouse. A cordless mouse uses radio waves to communicate with the computer.

A trackball is used instead of a mouse on notebook computers. The main part of this device is a ball built into the keyboard. The ball has the same function as the ball of a mouse. Turning the ball by hand moves the pointer. Trackballs are also sold as peripherals.

A touchpad is a touch-sensitive area in front of the keyboard on a notebook computer. Touchpads are also sold as peripherals for desktop computers. Sweeping a finger on the surface of the touchpad moves the pointer on the screen. Tapping its surface performs the same action as clicking a mouse, and tapping twice is the same as double-clicking. A tap followed quickly by a sweep is the same as a click-and-drag.

A digitizing tablet may be used to write words or draw pictures directly into the computer. A stylus that looks like a ballpoint pen interacts with the surface of the tablet. When the user moves the stylus on the tablet the computer uses this information to draw images on the monitor corresponding to the motions of the stylus. A tablet may be as small as mouse pad or as large as a drafting table.

A touch screen can be described as a transparent tablet covering a computer’s display screen. Pressing the screen sends the corresponding position information to the computer. Some screens work with the touch of a finger. Others work with a pen-like tool that, like the tool used with a digitizing tablet, is called a stylus, but which contains no electronics.

A light pen is an electronic wand with a light-sensitive tip. The user touches the light pen to the monitor screen to make selections or to “draw” on the screen. Other input devices, such as the mouse, digitizing tablet, and touch screen, have largely replaced the light pen.

A joystick is a stick held in the hand with a trigger that often used to operate computer games, instructing the computer to move an object or character in particular direction on the screen. For example, tiling the joystick to the left might cause a computer-generated airplane to fly to the left, and pulling the trigger might activate a simulated weapon.