Information Technology

1. Information Technology Output Devices Lecture 6 Presented by Miss N. Nembhard

2. Output Devices • Receives an electrical signal and produces data or information. • The purpose of an output device is to translate data and information from electrical impulses (digital) to human readable format.

3. The Monitor • An output device which is necessary for the computer to display an output to the user. • The video display Adapter (video card) on the motherboard allows information to leave the processor and appear on the monitor.

4. Types of Printers 1.Liquid Crystal Display (LCD) • These monitors are much thinner and lighter than the bulkier CRT monitors. They also use a lot less energy. LCD monitors use to be very expensive but the prices have fallen drastically. 2. Cathode Ray Tube (CRT) • These are bulky monitors that look like old fashioned TVs. They are usually much cheaper than LCDs.

5. Terms Associated with the Monitor • Soft copy - copy of a file shown on the screen. It is intangible. • Pixel (Picture Element) - A single point (a dot) in an electronic image. The greater the number of pixels, the better the quality of the image.

6. Screen Clarity • Screen clarity depends on three things: • Resolution - Defines the clarity of an image and is specified as the number of dots per inch (dpi). Normally measured by the number of pixels that can be displayed. • Dot Pitch - Amount of space between pixels • Refresh Rate - Number of times per seconds that the pixels are recharged so that their glow remains bright.

7. The Printer • An output device that produces tangible copies or hard copies. • Hard copy -A tangible copy of a document produced by the printer e.g. flyer, letter, book, a card etc.

8. Categories of Printers • There are two main categories of printers: • Impact - the printing mechanism makes physical contact with the paper • Non-Impact - No physical contact between the printing mechanism and the paper.

9. Types of Impact Printers • There are two main types of impact printers: • Line Printers • Character printers Both types of impact printers print on perforated paper.

10. Line Printers • Printers that can use multiple print hammers to print an entire line of text at one time (or at least fast enough so that it appears so). • Disadvantages: • It cannot print graphics • The text it prints is of low quality

11. Character (Serial) Printers • Character or serial printers are printers that print a character at a time. • These are slower than line printers

12. Types of Character Printers • The two main types of character printers are: • Daisy wheel • Dot matrix printers

13. Daisy wheel • Daisy wheel printers – uses a wheel containing characters that rotates until the right character is facing the paper. • Although it prints high quality text, it cannot print graphics. Printing different types of font is also impractical since the wheel have to be changed in order to get a different font.

14. Dot Matrix Printer • The dot matrix printer have a head capable of firing tiny pins arranged in a matrix. As the print head moves back and forth, these pins strike the ribbon causing dots to be made on the paper. • These same dots can be used to print text as well as graphics • Some dot matrix printer can also print in color.

15. Dot Matrix Printers • They are used to print bills or forms that require carbon copies • Print special reports that require large continuous sheets some payroll and accounting sheets

16. Advantages of Impact Printers • Produces carbon copies of information being printed. • Inexpensive • Maintenance is inexpensive • Uses ink ribbons which are inexpensive

17. Disadvantages of Impact Printers • They are relatively slow • Draft quality is low • Ink ribbons have short lives • Noisy

18. Non Impact Printers • Non-Impact printers are printers that print using methods that do not involve striking the paper or an ink ribbon. • They are generally faster than most impact printers and quieter. • Some types are much more expensive than impact printers • Non-Impact printers do not use perforated paper

19. Types of Impact Printers • Inkjet printer • Laser printer • Thermal printer

20. Inkjet Printer • They squirt very small drops of ink on the paper in order to produce text and images. • They are commonly used in the home. • The are relatively cheap and produce high quality output at relatively high speed.

21. Laser Printer • A very fast printer that utilizes a laser beam along with a toner and a photoconductive rotating drum in order to produce very high quality output. • They are faster than inkjet printers • They are called page printers because it appears that they print an entire page at one time. • They are usually limited to office use because they are expensive.

22. Thermal Printers • They print by using heat. Some thermal printers use special heat-sensitive paper. • Heat is applied to the paper to form text and graphics • They have low maintenance cost since there is not the need to buy toner or print ribbon. • Some fax machines print using this method.

23. Advantages of Non-impact Printers • Produce high quality and high speed output • Almost noiseless • uses toner or ink cartridges, which are longer lasting

24. Disadvantages of Non-Impact Printers • Printers are usually expensive • Maintenance is also expensive • Toner is relatively expensive

25. Types of Printers • Dot Matrix: Impact printer • Inkjet: Non-Impact printer • Laser: Non-Impact printer

26. Plotter • Output device used to produce high quality drawings (images) and large hard copies e.g. posters. • Chosen over printers when high quality graphics and making large clear posters.

27. Plotters continued • Have built in microprocessors that converts characters and instructions into a series of coordinates, which the plotter then plots. • Produces high resolution images • Used by engineers, graphic designers, architects.

28. Speakers • Sound cards code audio signals into signals which can be used by the speaker, which in turn amplifies them. • Sub woofers - Speaker system that can be attached to your PC and speakers to enhance your sound effects.

29. Computer Output on Microfilm • Computer output on film rather than on paper. • Stores images on plastic films. • Images are held in a much reduced format.

30. Microfilm • Reels of films used to store data or images. • Primarily used to store for preserving journals and news papers and hold hundreds of prints on one film.

31. Microfiche • Flat individual sheets of film. • Primarily used to preserve government document and college catalogues. A special reader is needed to view the pages stored.

32. Multimedia Projector • Works with a variety of media, e.g. computer, camera, printer and the scanner. • It projects and magnifies images on a large white screen normally mounted on a wall some distance from the computer.

33. Other Types of Output Devices • Audio output devices for example: • Speakers • Head-phones • Earphones

34. Human Readable vs Machine Readable • Human Readable - output devices that produce hard or soft copies of information or data that can be read and interpreted by humans • Machine readable - devices that output in a form only a computer can process.

35. Activity • Explain the following terms associated with the monitor: • Resolution • Pixel • Dot Pitch • Refresh Rate • Identify the two main types of printers • Give an example of each of the two types of printers you identified above. • Differentiate between the terms : “hardcopy” and “softcopy”.

36. References • Information Technology for CSEC, Kelvin Skeete & Kyle Skeete