1. 6.1Input Device Input Device The hardware that allows users to enter data into a computer and converts the data into a computer-readable form. microphone keyboardmouse

2. 6.1Input Device Keyboards Allow users to enter data or commands into a computer and convert the pressed keys into electrical signals Letter key Modifier key

3. 6.1Input Device Pointing Devices Allow users to control the cursor or pointer on a graphical user interface and trigger an action A pointer is a small symbol on the screen an arrowa pointing handan I-beam With a pointing device, you can position the pointer to select or move an item on the screen.

4. 6.1Input Device Select an item in a menu. Move an item from one place to another.

5. 6.1Input Device Mouse Uses multidirectional mechanism to register its motion Mechanical mouse Tracks rolling direction of the ball on its underside Optical mouse Optical sensor tracks its movement scrolling wheel buttons

6. Optical mouse Mechanical mouse 6.1Input Device Mouse Top viewBottom view Top view Bottom view

7. 6.1Input Device Trackball It is like an inverted mouse You move the pointer by rolling the ball. The buttons next to the ball works the same as those on a mouse. Has the advantage of saving space since it remains stationary during operation.

8. 6.1Input Device Touchpad A touch-sensitive plate usually found on a notebook computer. You move the pointer by dragging fingertip on touch pad. Tapping the pad is equivalent to clicking buttons on a mouse.

9. 6.1Input Device Trackpoint A small stick usually positioned somewhere between the keys. Pressure-sensitive, moving pointer in the direction you push in.

10. 6.1Input Device Joystick A pointing device designed for playing computer games The vertical lever controls the movement of the pointer. Most joysticks contain trigger buttons that can be used to perform certain actions in a computer game.

11. 6.1Input Device Touch Screen A video display device that has a transparent, touch-sensitive layer The user can interact with the computer by pressing the icons or figures on the screen. Widely used in information kiosks, personal digital assistants and notebook computers.

12. 6.1Input Device Digitizing Tablet Allows users to draw and sketch directly into a computer Detects the movements and pressure of pen-like stylus and converts them into digital signals Widely used in graphic design and engineering

13. 6.1Input Device Scanners Create digital images of source documents Operation: Projects light onto scanned object Captures the reflected light Converts the signals into a bitmap image

14. 6.1Input Device Scanners The quality of a scanned image is determined by: Resolution Determines the sharpness of picture Measured in dots per inch (dpi) Resolution Determines the sharpness of picture Measured in dots per inch (dpi) Color depth Determines how many colors are used to represent each dot Color depth Determines how many colors are used to represent each dot Accuracy Depends on the likeness of the scanned image in terms of color and shape to the original object Accuracy Depends on the likeness of the scanned image in terms of color and shape to the original object

15. 6.1Input Device Scanners Optical character recognition (OCR) software can read a scanned image of text document and translate it into a text file.

16. 6.1Input Device Optical Readers Read predetermined characters, marks or codes and translate them into digital data that a computer can use. Bar Code Readers Captures images of bar codes and translates them into numbers.

17. 6.1Input Device Optical Readers Optical Mark Readers Used with optical mark recognition (OMR) software OMR recognizes specific hand-written marks. Commonly applied on multiple choice answer sheets.

18. 6.1Input Device Microphones Allows users to record sound into a computer Usually connected to a sound card installed on the motherboard Can be used with speech recognition software, which translates vocal speech into text or commands.

19. 6.1Input Device Digital Cameras Uses a light-sensitive processor chip to capture scenes and turn them into digital image Image files are stored in a memory card. The amount of memory space taken by an image depends on the compression ratio, the file format and image resolution. The larger the number of light-sensitive photosites in the processor chip, the higher the resolution of the image.

20. 6.1Input Device Digital Camcorders Uses a light-sensitive processor chip to capture the moving images and store them as a sequence of high-quality digital images The digital images can be transferred to the computer directly without quality loss.

21. 6.1Input Device Digital Camcorders Uses a light-sensitive processor chip to capture the moving images and store them as a sequence of high-quality digital images The digital images can be transferred to the computer directly without quality loss.

22. 6.2Output Device Output Device The hardware that translates information processed by the computer into a form that humans can understand Visual display Speakers Printer

23. 6.2Output Device Visual Display Unit (VDU) Allows a user to view computer output instantly on a screen Liquid crystal display (LCD) monitor Cathode ray tube (CRT) monitor

24. 6.2Output Device Visual Display Units (VDU) Pixel The smallest display unit of the monitor screen Represents one dot of an electronic image by displaying a certain colour and colour intensity Size of monitor Determined by the diagonal length of the screen

25. 6.2Output Device Visual Display Units Quality of a monitor’s display Determined by: Resolution The number of pixels a monitor can display. At higher resolution, a larger work area can be displayed, but the text and images will appear smaller. Resolution The number of pixels a monitor can display. At higher resolution, a larger work area can be displayed, but the text and images will appear smaller. Dot Pitch The vertical distance between each pixel on a screen. The smaller the dot pitch, the sharper the displayed image. Dot Pitch The vertical distance between each pixel on a screen. The smaller the dot pitch, the sharper the displayed image.

26. 6.2Output Device Visual Display Units Dot pitch 768 pixels 1024 pixels Resolution = 768 x 1024

27. 6.2Output Device Visual Display Units Contrast Ratio The measurement of the difference between the brightest white and the darkest black e.g. 600:1 Contrast Ratio The measurement of the difference between the brightest white and the darkest black e.g. 600:1 Refresh Rate The rate for a monitor to redraw the display e.g. 75 Hz Refresh Rate The rate for a monitor to redraw the display e.g. 75 Hz

28. 6.2Output Device Visual Display Units A comparison between LCD monitors and CRT monitors Advantages of LCD monitors Advantages of CRT monitors Slimmer and lighter Clearer display Lower radiation emission Lower power consumption Cheaper Higher contrast ratio Higher refresh rate

29. 6.2Output Device Speakers Used to produce audio signals for a computer system The sound card converts digital audio signals into analogue signals for output through the speakers. Speakers with subwoofer produces better base frequencies. Speakers Speakers with subwoofer

30. 6.2Output Device Printers Allow users to produce text and graphics on a physical medium such as paper or transparency film The performance of a printer is mainly determined by: Resolution Measured by the number of dots per inch (dpi) The higher the dpi, the sharper the image. Resolution Measured by the number of dots per inch (dpi) The higher the dpi, the sharper the image. Printing Speed Measured either by the number of pages per minute (ppm) or characters per minute (cps) Printing Speed Measured either by the number of pages per minute (ppm) or characters per minute (cps)

31. 6.2Output Device Printers Some common types of printers: Dot-matrix printer Plotter Laser printer Ink-jet printer

32. 6.2Output Device Printers Comparison of mechanism Type of printer Mechanism Dot-matrix printer Strike pins on an ink ribbon to form a dotted image on the paper. Ink-jet printer Form images by spraying tiny ink drops onto paper. Laser printer Use a laser beam to produce an electrostatic film on a drum. The toner stuck on the charged area is then transferred and fused onto paper.

33. 6.2Output Device Printers Comparison of mechanism Type of printer Mechanism Thermal printer Produce a printed image by selectively heating thermal paper when the paper passes over the thermal print head. Plotter Similar to ink-jet printers

34. 6.2Output Device Printers Comparison of features Type of printer Printing quality Printing speed Printing Cost Dot-matrix printer Low Ink-jet printer HighMediumHigh Laser printerHigh Medium PlotterSimilar to ink-jet printers

35. 6.2Output Device Printers Type of printer Other features Dot-matrix printer Ideal for printing multi-part forms Ink-jet printer Uses a black cartridge and one or more colour cartridge to produce high-quality color printouts Laser printer Has to store the whole image of the page before printing process begins Thermal printer Used in point of sale systems Plotter Creates high-quality or large-format printouts

36. 6.2Output Device Multifunction Printers Combines the functions of Printer Scanner Photocopier Fax machine Telephone Advantages Takes up less space Cheaper than buying all devices separately

37. 6.2Output Device Data Projectors Used to project the computer display onto a large screen The performance is mainly determined by the panel resolution and the brightness Two common types of projectors DLP projectorLCD projector

38. 6.2Output Device Data Projectors Comparison between LCD and DLP projector Type of projector MechanismConsequence LCD projector Uses built-in light source to project the image on its LCD panel onto screen Uses light less efficiently DLP projector Builds images on the screen by digitally controlling the reflections on tiny mirrors Uses light more efficiently Can be seen clearly even in well-lit room