Make your own free website on




  0utput is data that has been processed into a useful form called information. That is, a computer     processed input into output. Computers generate several types of output, depending on the hardware and software being used and the requirements of the user. You may choose to display or view this output on a monitor, print it on a printer, or listen to it through speakers or a headset.  

 Four common types of output are:

                                 I.      Text

                               II.      Graphics

                              III.      Audio

                            IV.      Video




Consists of characters that are used to create words, sentences, and paragraphs. A character is a letter, number, punctuation mark, or any other symbol that requires one byte of computer storage space.



Are digital representations of non-text information such as drawings, charts, and photographs? Graphics also can be animated, giving them the illusion of motion.



Is music, speech, or any other sound? Recall that sound waves, such as the human voice or music, are analog. To store such sounds, a computer converts the sounds from a continuous analog signal into a digital format. Most output devices require that the computer convert the digital format back into analog signals.





Output is data that has been processed into a useful form called information. That is a computer processes input into output. Computers generate several types of output, depending on the hardware and software being used and the requirement of the user. You may choose to display or view this output on a monitor, print it on a printer or listen to it though speakers or a headset. Four common types of output are text, graphics, audio and video. 




Text consists of characters that are used to create word, sentences and paragraphs. A character is a letter, number, punctuation mark or any other symbol that requires one byte of computer storage space.

Graphics are digital representations of context information such as drawings, charts and photographs. Graphics also can be animated, giving them the illusion of motion. Displaying a series of still images in rapid sequence creates animation.

 Audio in music, speech or any other sound. Recall that sound waves, such as the human voice or   music, are analog. To store such sound, a computer converts the sounds from a continuous analog signal into a digital format. Most output devices require that the computer convert the digital format back into analog signal. Video consists of images that are played back at speeds that provide the appearance of full motion. Video often is captured with a video input devices such as a camera or VCR.A video capture card converts an analog video signal into a digital that a computer can understand. The digital signal then is stored on the computer’s hard disk.



An output device is any computer component capable of conveying information to a user. Commonly used output devices include display devices, speakers, headset, data projector, facsimile machines and multifunction devices.  


A data projector takes the image that displays on a computer screen and projector it into a screen so that an audience of people can see the image clearly. Data projectors can be large devices attached to ceiling or wall in an auditorium, or they can be small portable devices. Two types of smaller, lower-cost units are LCD projector s and DLP projectors.

An LCD projector, which uses liquid crystal display technology, attaches directly to a computer and uses its own light source to display the information shown on the computer screen. Because LCD projectors tend to produce lower-quality images, some users prefer to use a DLP projector for shaper, brighter images.

A digital light processing (DLP) projectors uses tiny mirrors to reflect light, producing crisp, bright, colorful images that remain in focus and can be seen clearly even in a well-lit room.



The most common application of liquid crystal technology is in liquid crystal displays (LCDs). From the ubiquitous wristwatch and pocket calculator to an advanced VGA computer screen, this type of display has evolved into an important and versatile interface.

A liquid crystal display consists of an array of tiny segments (called pixels) that can be manipulated to present information. This basic idea is common to all displays, ranging from simple calculators to a full color LCD television.

Why are liquid crystal displays important? The first factor is size. As will be shown in the following sections, an LCD consists primarily of two glass plates with some liquid crystal material between them. There is no bulky picture tube. This makes LCDs practical for applications where size (as well as weight) is important.

In general, LCDs use much less power than their cathode-ray tube (CRT) counterparts. Many LCDs are reflective, meaning that they use only ambient light to illuminate the display. Even displays that do require an external light source (i.e. computer displays) consume much less power than CRT devices.

Liquid crystal displays do have drawbacks, and these are the subjects of intense research. Problems with viewing angle, contrast ratio, and response time still need to be solved before the LCD replaces the cathode-ray tube. However with the rate of technological innovation, this day may not be too far into the future.

We will restrict this discussion to traditional nomadic LCDs since the major technological advances have been developed for this group of devices. Other LC applications, such as those employing polymer stabilization of LC structure, are discussed in the appropriate section covering those materials.


CRT MONITORS               

A CRT monitor, or monitor is a display device that consists of a screen housed in a plastic or metal case. A color monitor display text, graphics and video information in color. Color monitor are used widely with all types of computers because most of today’s software is designed to display information in color.

Monitor that display only one color are considered monochrome. A monochrome monitor display text, graphics and video information in one color (usually white, amber or green) on a black background. Because monochrome monitors are less expensive than color monitors, some organizations use them for applications that do not require color or detailed graphics, such as order entry. To enhance the quality of their graphics display, some monochrome monitors use gray scaling, which involves using many shades of gray from white to black to form the images.

Like a television set, the core of a CRT monitor is a large glass tube called a cathode ray tube (CRT). The screen, which is the front of the tube, is coated with tiny dot of phosphor material that glows when electrically charged. Inside the CRT, an electron beam moves back and forth across the back of the screen, causing the to glow, which produces an images on the screen.

Each dot, called a pixel (short for picture element), is a single point an electronic image. Monitors consist of hundreds, thousands or millions of pixels arranged in rows and columns that can be used to create images. The pixels are so close together that they appear connected.

CRT monitors are used with a variety of computers. The CRT monitors used with desktop computers are available in a number of sizes, with the more common being 15, 17, 19 and 21 inches. The size of a monitor is measured diagonally from corner to corner.

Most monitors are referred to by their viewable size, which is the diagonal measurement of the cathode ray tube inside the monitor and is larger than the actual viewing area provided by the monitor.



The computer monitor, screen or VDU (visual Display Unit) is the most common output devices.



Relatively cheap and reliable, can display text and graphics in a wide range of colors. They are also quiet and do not waste paper.

No permanent copy to keep and unsuitable for users with visual problems.

Screen sizes are measured diagonally and are still quoted in inches. Popular size are 15 inches (38 cm) and 17 inches ( 43 cm ). Larger monitor make working at a computer easier on the eyes and are essential for use in DTP (Desktop Publishing) and CAD work.Most computers are similar in many ways to a television. They use cathode ray tubes

(CRTS) containing an electron gun at the back the tubes which fires electrons at groups of phosphor dots coating the inside of the screen. On a color monitor each group of phosphor dots is made up of green, blue, and red dot makes up a pixel of visible light. By varying the intensity of each of these primary colors, the whole pixel will appear to the human eye as any colored desired.

The quality of a monitor’s display depends largely on its resolution, dot pitch and refresh rate. The resolution, or sharpness and clarity, of a monitor is related directly to the number of pixel it can display. Resolution is expressed as two of pixels:

1)   The number of columns of pixel

2)   The numbers of pixel a monitor can display

A monitor with a higher resolution display a greater number of pixels, a higher resolution causes images to display smaller on the screen. The ideal monitor resolution to use is a matter of preference. A higher resolution is desirable for graphic application; a lower resolution usually is satisfactory for application such as word processing.


GAS PLASMA MONITORS.               

For even larger displays, some large business or power users prefer gas plasma monitors, which can measure more than 42 inches and hang directly on a wall. Gas plasma monitors use gas plasma technology, which substitutes a layer of gas the liquid crystal material in an LCD monitor. When voltage is applied, the gas glows and produces the pixels that form an image. Gas plasma monitors offer larger screen sizes and higher display quality than LCD monitors but are much more expensive. 



The quality of a monitor’s display depends largely on its: 


The resolution or sharpness and clarity, of a monitor are related directly to the number of pixels it can display. Resolution is expressed as two separate numbers: the number of columns of pixels and the number of rows of pixels a monitor can display.

Dot pitch.

Pitch is a measure of image clarity. The dot pitch is the vertical distance between each pixel on a monitor. The smaller the distance between the pixels, the sharper the displayed image.

Refresh rate.

A monitor’s refresh rate should be fast enough to maintain a constant, flicker-free image. A slower refresh rate causes the image to fade and then flicker as it is redrawn, which can headaches for user. Refresh rate is measured according to hertz, which is the number of times per second the screen is redrawn.



High-definition television (HDTV) is a type of television set that works with digital broadcasting signals and support a wider screen and higher resolution display than a standard television set. When you use a standard television set as a monitor for your computer, the output must be converted to an analog signal that can be displayed by the television set.   

With HDTV, the broadcast signals are digitized when they are sent. Digital television signals provide two advantages over analog signals. First, digital signals produce a higher-quality picture. Second, many programs can be broadcast on a single digital channel, whereas only one program can be broadcast on an analog channel. Because HDTV is capable of receiving text, graphics, audio and video, you can use HDTV as a monitor while browsing the Internet. When the cost of HDTV becomes more reasonable, home user will begin to use it as their computer’s display device.



Printers are primary output devices used to generate information from the computers. Reports, sales receipts letters and memos are all examples of output by the computer through the printer. These output are often referred to as “Hard Copies” or “Printout” in computer jargon.

Printers are very similar to electric typewriters minus the keys. With speed taken into consideration, printers can be classified into character line, or page printers.

Character printers are the slowest printers since they print character by character. There are two types of character printers:

          Dot-Matrix printers

         Letter-Quality printers

Character is printed line-by-line, hence increasing printing speed that uses electromechanical parts. Page printers are high speed, non-impact printers with printing rates so high that output appears to be printed a page at a time. Electrostatics printers form character on chemically treated paper by using charge pins.

Laser beam printers use a combination of laser beam and electrographic techniques to create printed output at tremendous speed.




Ř      Limited to situations where carbon copies are needed and the quality is not too important.

Ř      Typical uses might be in warehouse where duplicate copies of orders need to produce quickly and cheaply.

Ř      The printing quality is low because of this impact these printers can be quite noise.

Ř      The purchase cost is low and the running costs are very low.

Ř      Can print fairly quickly, if you remember that multiple copies are being printed in one print run.

Ř      Robust and can operate in harsh environments.

Ř      If several sheets of self-carbonating paper are placed into the printer then the impact will produce multiple copies.



A popular choice for home and school use where small amounts of printing are done    

The ink cartridges can be expensive so running costs can be high.

 Speed is slow compared to a laser printer.

Relatively inexpensive and produce high quality black and white or color printing.



 Common wherever fast, high quality printing is required.

  Non color laser printers are more expensive than ink-jet printers (but the difference is narrowing).

 Color laser printers are ‘considerably more expensive’ (but their speed and high quality output means they are becoming more popular).

Quiet and fast and produce high quality printouts.

Running cost are low because although toner cartridges are expensive to replace, they last a long time.





In any sound system, ultimate quality depends on the speakers. The best recording, encoded on the most advanced storage device and played by a top-of-the-line deck and amplifier, will sound awful if the system is hooked up to poor speakers. A system's speaker is the component that takes the electronic signal stored on things like CDS, Tapes, and DVDs and turns it back into actual sound that we can hear.



In this article, we'll find out exactly how speakers do this. We'll also look at how speaker designs differ, and see how these differences affect sound quality. Speakers are amazing pieces of technology that have had a profound impact on our culture. But at their heart, they are remarkably simple devices.



A device that draws pictures on paper based on commands from computer. Plotter differs from printer in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printer can only simulate lines by printing a closely spaced series of dot. Multicolor plotter use different colored pens to draw different colors.  

In general, plotters are considerably more expensive than printer. They are used in engineering application where precision is mandatory.  Graphics plotter – the flat- bed plotter uses high precision motors to draw on paper with colored ink pen. The motors move an arm across the paper in the  ‘x’direction and a pen unit up and down the arm in the ‘y’ direction. An electromagnet lifts and drops the pen onto the paper. 

Plotters are often used in science and engineering application for drawing building plans, printer circuit boards and machine parts. They are fast and accurate but relatively expensive compared to printer. They can produce far larger printouts than standard printer, up to the size of a small room.          



A facsimile (fax) machine is a device that transmits and receives documents over telephone lines. The documents can contain text, drawings, or photographs, or can be handwritten. When sent or received via a fax machine, these documents are known as faxes. A stand-alone fax machine scans the original documents, converts the image into digitized data, and transmits the digitized image (Figure 5-34). A fax machine at the receiving end reads the incoming data, converts the digitized data into an image, and prints or stores a copy of the original image.

Fax capability also can be added to your computer using a fax modem. A fax modem is a communications device that allows you to send (and sometimes receive) electronic documents as faxes (Figure 5 –35). A fax modem transmits computer-prepared documents that have been digitized with a scanner or digital camera. A fax modem is like a regular modem except that is designed to transmit documents to a fax machine or to another fax modem.

 When a computer (instead of a fax machine) receives a fax, you can view the document on the screen or print it using special fax software. The quality of the viewed or printed fax is less than that of a word processing document because the fax actually is a large image. If you have optical character recognition (OCR) software, you also can edit the document. A fax modem can be an external peripheral that plugs into a port on the back of the system unit or an internal card that is inserted into an expansion slot on the motherboard. In addition, most fax modems function as regular modems.