3.1. Output devices

This is any type of hardware component that conveys information one or more people.

Commonly used output devices include display devices, printers, speakers and headsets, fax machines and fax modems, multifunction peripheral data projectors e.t.c.

Output is data that has been processed into useful form. The computer processes input (data) into information (Output). 

The out put, which can be easily understood and used by human beings, are of the following two forms:

1.        Hard Copy: The physical form of output is known as hard copy. In general, it refers to the recorded information copied from a computer onto paper. Hard copy output is permanent and a relatively stable form of output. This type of output is also highly portable. Paper is one of the most widely used hard copy output media.

2.        Soft Copy: The electronic version of an output, which usually resides in computer memory and/or on disk, is known as soft copy. Unlike hard copy, soft copy is not a permanent form of output. It is transient (lasting for a short period of time) and is usually displayed on the screen. This kind of output is not tangible, that is, it cannot be touched. Soft copy output includes audio and visual form of output, which is generated using a computer

 

Following are few of the important output devices, which are used in Computer Systems:

Monitors

Monitor commonly called as Visual Display Unit (VDU) is the main output device of a computer. It forms images from tiny dots, called pixels,that are arranged in a rectangular form. The sharpness of the image depends upon the number of the pixels.

There are two kinds of viewing screen used for monitors:

Ø  Cathode-Ray Tube (CRT). In the CRT, display is made up of small picture elements called pixels for short. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form whole character, such as the letter 'e' in the word help.

Ø  Flat-Panel Display MonitorThe flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement compared to the CRT. You can hang them on walls or wear them on your wrists. Current uses for flat-panel displays include calculators, video games, monitors, laptop computer, graphics display.The flat-panel display are divided into two categories:

1.        Emissive Displays - The emissive displays are devices that convert electrical energy into light.

Example are plasma panel and LED (Light-Emitting Diodes).

2.        Non-Emissive Displays - The Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. Example is LCD (Liquid-Crystal Device)

 

Printers.

A printer prints information and data from the computer onto a paper. The quality of a printer is determined by the clarity of a print it can produce, that is, its resolution.

Printers are divided into two basic categories: impact printers and non-impact printers. As their names specify, impact printers work by physically striking a head or needle against an ink ribbon to make a mark on the paper. This includes dot matrix printers, daisy wheel printers, and drum printers. In contrast, inkjet and laser printers are non-impact printers. They use techniques other than physically striking the page to transfer ink onto the page.

 

Factors considered before buying a printer

Ø  The number of pages per minute (ppm) the printer can print.

Ø  The memory size of the printer i.e. at least 2 MB Ø The price of the cartridge or tonner.

Ø  The availability of cartridge or tonner.

Ø  The price of the printer.

Ø  The purpose for which the printer is going to be put to use

 

 

Advantages of Hard copy over soft copy

Ø  A hard copy can easily be accessed by both the rich and poor readers.

Ø  It cannot easily be changed without tracing.

Ø  It can be read off-line namely without a computer.

Ø  It is cheaper compared to softcopy, which requires computer devices to be able to read the information / data.

Ø  Hard copies last longer if stored in a safe place compared to softcopy, which must be all the time changed with the technological developments taking place.

 

Speakers and headsets

An audio output device is a component of a computer that | produces music, speech, or other sounds such as beeps. Two commonly used audio output devices are speakers and headsets. Many personal computers users add stereo speakers to their computers to generate a high-quality sound.

Fax machines and Fax Modems

A fax machine is a device that transmits and receives documents over telephone lines. A fax modem is a modem that allows you to send (and sometime receive) electronic documents as faxes

 

Data projectors

These are devices that take the images from a computer screen and projects it onto a larger screen and projects it onto a larger screen so an audience of people can see the image clearly.

Qn1: Mention devices which can be classified as both input and also output computer hardware.

1.        Touch Screen - a touch-sensitive display device you touch words, pictures, numbers, letters, or locations identified on the screen.

2.        a floppy diskette drive - a device used for both reading and writing data to and from a floppy disk

3.        Optical Disk Writer - a device used for both reading and writing data to and from optical disks such as CDs, DVDs and Blu-ray disks

4.        a hard disk drive - a device used for both reading and writing data to and from a Hard disk

5.        USB flash drive - used for both reading and writing data to and from Flash disks

6.        Modem