Input & Output Part II

1. Input & OutputPart II Bayram Güzer

2. Output • Output provides the information for the user. • Computer systems have several kinds of outputs. • Main output units in computer systems are screens and printers.

3. Output • Example: Suppose that you went to a travel agency and asked for reservation on an flight connection. The travel agent will enter data and make few queries to find available flights and the results will be displayed on a screen. If reservation is made, then the agent can get a printed output for tickets, traveler's itinerary and the invoice.

4. Computer Screen Technology • In computer systems, screen is one of the main elements. • When you enter data, it appears on the screen. • The screen is a part of the computer monitor which also includes electrical components, monitor stand and etc… • Soft copy is the screen output because it is intangible and temporary • Hard copy is produced by printer on a paper and it is tangible and permanent

5. Common Forms of Monitors • Cathode Ray Tube (CRT) • Flat-Panel Screens • Smart Displays • Terminals

6. CRT Monitors • Display text and graphics • Most are in color • Some monochrome monitors are used in applications that have no need for color or graphics • Uses of monochrome monitors are in business applications such as customer inquiry or order entry systems that no color is needed. • Graphics card converts signals from the control unit into the image the user sees

7. CRT Monitors • Most CRT screens uses a technology which is called as raster scanning. • Raster scanning is a process of sweeping (süpürmek) electron beams from back of the screen. • The screen display has a phosphorous coating that glows whenever it is hit by a beam of electrons. • But the phosphorus doesn’t glow for very long, so the image must be refreshed often. • If the screen is not refreshed often enough, the fading screen image appears to flicker (titreme).

8. CRT Monitors • Scan rate • The frequency with which the image is refreshed • The sufficient rate is 80 or 100 times per second • Interlaced is another method for scanning the screen. • In interlaced fashion, first the odd-numbered lines and then the even-numbered lines are scanned. • This requires a lower refresh rate without producing any flickering. • When animations appear in monitors, interlacing can create irritating flutter (dalgalanma) effect. For that reason, most screens are today announced as non-interlaced which means all lines are scanned in order.

9. CRT Monitors • A computer screen is divided into dots that is called as addressable because they can be addressed individually. • Each dot can be illuminated individually on the screen. • Each dot is potentially a picture element or a pixel. • Resolution defines clarity (açıklık) of screen • Measured in pixels (picture elements) • The more pixels, the higher the resolution • There are some graphics standards exist

10. CRT Monitors • Dot pitch • It is the amount of space between dots • If the dot pitch is smaller, the image is sharp-edged (keskin kenarlı) • Most computers come with built-in graphics compatibility. • But if the computer doesn’t have built-in graphics, there will be a need for graphics card or graphics adapter board.

11. Graphic Standards • Defines the agreement on resolutions, colors, other issues related to displaying graphics • Super Video Graphics Adapter (SVGA) is most common standard • Provides 800 (horizontal) x 600 (vertical) pixels on the display • Other varieties of SVGA exist • 1024 by 768 • 1280 by 1024 • 1600 by 1200 • Support 16 million colors • The number of colors that can be displayed depends on amount of video memory

12. Graphic Standards • Extended Graphics Array (XGA) is a high resolution graphics standard designed to replace older standards. • It provides more simultaneous colors • It allows monitors to be non-interlaced.

13. Flat Screen Monitors • Liquid crystal display (LCD) • Originally used for laptops, but making their way to desktop computers by becoming bigger every day. • Very thin (only a few inches) • Produce sharper text images than CRTs • Easier on eyes than CRTs • More expensive than CRTs

14. Flat Panel Technologies • Active-matrix • Uses many thin-film transistors (TFT) • Produces brighter image and can be viewed from wider angles • Passive-matrix • Uses fewer transistors • Cheaper and uses less power • Gas plasma • Supports very large displays • Has brilliant color display • Viewable at very wide angles

15. Smart Displays • Based on flat-panel technology • Each contains its own processor • Wireless transmitter-receiver allows user to control desktop from anywhere in the house • Idea was announced by Microsoft as Mira in 2002, but the project was cancelled in December 2003.

16. Terminals • A screen can be part of a terminal attached to a large computer. • A terminal consists of an input device, an output device, and a communications link to the main computer. • Smart terminals are the terminals which has some processing ability of their own CPU. • Bank tellers use terminals to communicate directly with a central computer to determine bank balances and other information.

17. Printers • A printer is a device that produces information on paper output. • Old printers were producing only letters and numbers. • Most printers have two orientation setting which is portrait and the landscape. • Portrait mode prints out on vertical side • Landscape mode prints out on horizontal side

18. Printers • There are two ways for printing an image on paper. • Impact method • Uses some sort of physical contact with the paper to produce an image • Physically strike (hit)to paper, ribbon and print hammer together • Line Printers: Impact printers that print entire line at a time is called as line printers. It is typically used with mainframe computers for printing lengthy reports.

19. Printers • There are two ways for printing an image on paper. • Impact method • Dot-matrix printers: Has print head consisting of one or more columns of pins • Pins form characters and images as patterns of dots

20. Printers • There are two ways for printing an image on paper. • Nonimpact method • Places an image on a page without physically touching the page. • Major nonimpact technologies are laser and ink-jet printers. • Laser printers use a light beam to help transfer images to paper. • Laser printers produces high-quality output at very fast speeds.

21. Printers • There are two ways for printing an image on paper. • Nonimpact method • Ink-jet printers spray ink from multiple jet nozzles • Can print in both black & white and different colors. • Print quality and speed is not matching that of a laser printer. • Less expensive than laser printers but requires high quality paper so ink doesn’t spread

22. Voice Output • Speech synthesis is the process of enabling machines to talk to people. • Voice synthesizers convert data to vocalized sounds that is understandable to humans. • Two approaches exist • Synthesis by analysis - analyzes actual human voice, records and plays back as needed • Synthesis by rule - uses linguistic rules to create artificial speech • Used in automated telephone-based customer service applications • Useful when an inquiry would be followed by a short reply, such as a balance inquiry, automatic telephone voice survey.

23. References • Capron, H. L. (2000). Computers Tools for an Information Age.(6th ed.). New Jersey, USA: Prentice Hall. • Long, L. & Long, N. (2001). Computers. (8th ed.). New Jersey, USA: Prentice Hall. • Smart Display. (n.d.). Retrieved 01 November 2009 from http://www.amazon.com/ViewSonic-airpanel-V150-Smart-Display/dp/B00007A5K0 • Smart Displays. (2008). Retrieved 01 November 2009 from http://en.wikipedia.org/wiki/Smart_Display