1 Technology In Action

2 Chapter 2 Looking at Computers: Understanding the Parts

3 Chapter Topics Hardware components Input devices Output devices System unit Ergonomics

4 A Computer Is… A device that accepts input, processes data, stores data, and produces output

5 A Computer Is… A collection of hardware and software assembled for a certain purpose –The physical parts of a computer are collectively known as hardware. –The programs or instructions used to tell the computer hardware what to do are software.

6 A Computer Is… Computers can store both data and instructions in memory. –Von Neumann architecture –A program is a set of hardware instructions which are loaded into memory –Storing multiple programs in memory allows you to switch between tasks –This ability distinguishes a computer from other simpler devices

7 Hardware System Unit Peripheral Devices System Unit Peripheral Devices

8 Input Devices Devices used to enter information or instructions into the computer –Keyboard –Mouse / pointing device –Microphone –Scanner –Digital camera Devices that are touched need to be cleaned regularly Scanner

9 Keyboard The QWERTY keyboard is standard on most PCs Enhanced features include number pad, function and navigation keys.

10 Dvorak Keyboard Puts the most commonly used keys at “home keys” Reduces distance of finger stretches

11 Specialty Keyboards Laptops PDAs Wireless Ergonomic Laptop Ergonomic PDA

12 Mouse Rollerball mouse –Less expensive –Harder to keep clean Optical mouse –Needs no mouse pad –Doesn’t need as much cleaning –More expensive Trackball –Less movement of the wrist –Stationary on desk Wireless mouse –can be either roller or optical –security issues Wireless Optical Trackball Standard

13 Inputting Sound Microphone Input –Teleconferencing –Voice over Internet –Voice Recognition Microsoft Voice Recognition

14 Input for the Physically Challenged Visually Impaired –Voice recognition –Keyboards with large keys –On-screen keyboards Motor control –Special trackballs –Head-mounted devices

15 Other Input Devices Scanners –Text (OCR) –Images –Bar codes –RFID tags Digital cameras –Images –Video Flatbed Handheld Camera Camcorder

16 Output Devices Retrieving information from the computer's memory for human use Output devices –Softcopy (video, sounds, control signals) –Hardcopy (print)

17 Monitor Types CRT Cathode Ray Tube –Less expensive –Use much more space –Uses more energy –Better viewing angles LCD Liquid Crystal Display –More expensive –Uses far less space –More energy efficient –Less viewable from an angle

18 CRT Monitors Uses picture tube (TV) technology Screen size – Diagonal measurement of the screen (15, 17, 19, 21 inches) Resolution – Sharpness of the image = the number of pixels that the screen can display (800 x 600, 1024 x 768, 1600 x 1200) Refresh rate – Speed at which the screen is refreshed (75Hz, 85Hz) Faster rate equals less flicker. Dot pitch - distance between pixels measured in mm (0.28, 0.32 mm) smaller is better

19 Liquid Crystal Display Liquid crystal sandwiched between two transparent layers form images Used for notebook computers, PDAs, cellular phones, and personal computers Polarizer Color filter Color filter glass Glass polarizer Backlight Liquid Crystal

20 CRTs vs. LCDs CRTs have wider viewing angles better color accuracy cheaper than LCDs slightly faster display Radiation a danger? LCDs are smaller and lighter take less power and give off less radiation have a larger viewable area

21 Other Video Output Touch-screen monitors double as both input and output devices. Data projectors project a computer image to a large screen for sharing with large groups.

22 Dot-matrix Printers Inkjet Multifunction Laser Plotter Thermal printer Impact printers –Dot-matrix Nonimpact printers –Inkjet –Laser –Multifunction Specialty printers –Plotters –Thermal printers

23 Nonimpact Printers Inkjet –Less expensive device –Full color printing –Slower in pages per minute (PPM) –More expensive per page in B&W Laser –More expensive device –Black and White (Color lasers are very expensive - CYMK) –Faster in PPM –Less expensive in B&W

24 Comparing Printers Speed - ppm Resolution - dpi Color / BW Memory - MB Cost of device Cost per page - ink or toner

25 Outputting Sound Voice synthesis –Stephen Hawking

26 Outputting Sound Speakers and Headphones

27 The System Unit Box that contains the central electronic components of the computer: –CPU/RAM/ motherboard –Expansion cards –Power supply –Storage devices

28 The Front Panel Drive bays Memory card reader Floppy drive Productivity ports Power button

29 The Back Ports for peripheral devices Types of ports: –Serial –Parallel –VGA –USB –Connectivity

30 Inside the System Unit Essential electronic components used to process data Types of components: –Power supply –Secondary storage –Motherboard –CPU –Expansion cards

31 The Motherboard CPU (chips) RAM Expansion cards

32 Central Processing Unit (CPU) Referred to as the “brains” of the computer Controls all functions of the computer Processes all commands and instructions Can perform billions of tasks per second

33 Memory Module Random access memory (RAM) Primary storage or main memory Stores instructions and data Temporary (volatile) storage Operates in nanoseconds (billionths of a second)

34 Expansion Cards Adds functions Provides new connections for peripheral devices Common types: –Sound –Modem –Video (VGA) –Network (NIC)

35 Secondary Storage Hard Disk Drive Stores data and program instructions Permanent (nonvolatile) storage Storage capacities up to 250 GB and higher Transfers data in milliseconds (slower than RAM!)

36 Setting it all up: Ergonomics Ergonomics refers to designing devices so they are comfortable and efficient to use Steps to follow: –Position monitor correctly –Use adjustable chair –Assume proper position while typing (RSI) –Take breaks –Ensure adequate lighting

37 The Digital Divide The Digital Divide is a social/political issue referring to the gap between people who have access to computers and the Internet and those who do not. Issues effecting this divide include age, economics, geographic location, etc… Attempted solutions - making computers available at public libraries, "One Laptop Per Child"

38 GIGO GIGO stands for “Garbage In, Garbage Out” If invalid data is entered in a computer program, the resulting output will also be invalid. If a computer asked you to enter a letter and you enter a number, the results you would get back would probably be messed up, or "garbage."