Trackball

A joystick is a pointing device used primarily for playing computer video games. A joystick usually has a square or rectangular plastic base to which is attached a vertical lever. Control buttons are located on the base and sometimes on top of the lever. The lever can be moved in multiple directions to control the movement of a cursor or other graphical object on the screen.

A light pen (or stylus) is a device like an ordinary pen that can be used to write text or draw an image directly on a special screen or to select information on the screen by pressing the light pen against the surface of the screen. Light pens are often used in computer-aided design and computer-aided manufacture (CAD and CAM) technology.

An optical scanner is used to enter graphics as well as typeset characters.This device reads images such as a picture or text on a printed page and translates them into binary numbers that the CPU can use. For example, a photograph can be scanned into a computer and then included in a text document created on that computer.

A microphone and a voice recognition unit can be also used to feed data into the computer. A microphone is a device converting sound into signals that can then be stored, manipulated, and reproduced by the computer. A voice recognition module is a device that converts spoken words into information that the computer can recognize and process.

(4) Output Devices

External devices that enable the user to see or hear the results of the computer's data processing are known as output devices. The results are output in either hardcopy or softcopy form. Hardcopy output can be held in your hand, such as paper with text (word or numbers) or graphics printed on it. Softcopy output is displayed on a monitor.

Monitor is a component with a video display or screen for viewing computer data, television programs, etc. Displays usually take one of two forms: a video screen with a cathode ray tube (CRT) or a video screen with a liquid crystal display (LCD).A CRT-based screen, or monitor, is similar to a television set.An LCD-based screen displays visual information on a flatter and smaller screen than a CRT-based video monitor. LCDs are often used in laptop computers.

Printers produce hard copy – a printed version of information stored in one of the computer's memory systems. Color ink-jet and black-and-white laser printers are the most common, though the decreasing cost of color laser printers has increased their use outside of the publishing industry³.

Most PCs also have audio speakers. These allow the user to hear sounds, such as music or spoken words that the computer generates.

A modem is an I/O device that connects a computer to a telephone line or cable television network and allows information to be transmitted to or received from another computer.

The digital signal sent from one computer is converted by the modem into an analog signal, which is then transmitted by telephone lines or television cables to the receiving modem, which converts the signal back into a digital signal that the receiving computer can understand.

Notes: ¹dozens – множество;

²single-sided disk – односторонний диск (с записью на одной стороне);

³publishing industry – издательское дело;