INPUT AND OUTPUT DEVICES

Devices that are used to get information into the computer are known as input devices. Input devices are used to convert information from a form used by humans into a form that is useable by computers.

Today, there are many different ways to get information into the computer, but the keyboard, a device that has been part of computer systems for many years, is still one of the most common input devices. The computer mouse is another input device that is becoming almost as common as the keyboard. It is referred to as a pointing device.

Unlike the keyboard — which is used to enter data one character at a time — a pointing device is used to move a pointer around on the display screen; when the screen pointer is resting on a name or an image on the screen, a button can be pressed to select the option or activity that is represented. In addition to the mouse, a number of other types of pointing devices for computers are also in use today.

Several other types of devices can be used to convert data into a digital form that can be used by computers. Data that exists in the form of characters or pictures on paper, as bar codes printed on packaging, or the magnetic patterns stored on credit cards can all be read by special devices and converted into a form that can be used by computers.

Output devices are used to get information out of the computer in a form useable by humans. The display monitor and the printer have long been the computer’s primary output devices. Today, they still represent the two most common ways to get information out of a computer, but the type and variety of both monitors and printers are in constant change.

Computer display monitors are the computer’s main output devices. Based on the same kind of technology used in television sets, the early display monitors could only produce characters in one color on a black background. Today, computer display monitors can present information in many colors and in many forms, including pictures.

These new output capabilities have led to a number of new computer applications that provide a way to create, display, and print pictures on the computer screen. Computer-aided design (CAD) programs are used to create engineering drawings and blueprints, paint and draw programs provide a set of software tools that can be used to create on-screen pictures, and presentation graphics programs can be used to turn numbers into charts and graphs.

Computer printers have also evolved as computer users sought better-printed representations of what they saw on the display screen. Data that is printed out on paper using a printer controlled by a computer is known as output, or hard copy.

Today, there are many different types of computer printers in use but they can generally be categorized as impact or nonimpact.

The most common type of impact desktop printer is the dot-matrix printer.

This type of printer places a dot on paper when one of a group of pins in the print-head strike through an inked ribbon. A series of these dots are used to represent characters or graphic images.

Another impact printer is the letter-quality printer. Letter-quality printers also place ink on paper by striking through an inked ribbon using strikers embossed with letters (like a typewriter).

Nonimpact printers produce an image on paper without using a striking device. Laser printers are a type of nonimpact printer. They have been available for some time, but they are now becoming more popular as the price of this printing technology has come down. Using a technology developed in dry-toner copying machines, laser printers are faster and quieter than impact printers and generally produce a high quality output.

Another nonimpact printer that is growing in popularity is the ink-jet. This type of printer places one dot at a time, but instead of using pins to strike through an inked ribbon this type places droplets of ink on the paper.

A number of other new nonimpact printer technologies are also now in use or under development.

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