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Technology In Action

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Technology In Action

Chapter 2Looking at Computers: Understanding the Parts

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Chapter Topics

• Hardware components

• Input devices

• Output devices

• System unit

• Ergonomics

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A Computer Is…

• A device that accepts input, processes data, stores data, and produces output

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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.

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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

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Hardware

•System Unit

•Peripheral Devices

System UnitSystem Unit

Peripheral DevicesPeripheral Devices

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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

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Keyboard

• The QWERTY keyboard is standard on most PCs

• Enhanced features include number pad, function and navigation keys.

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Dvorak Keyboard

• Puts the most commonly used keys at “home keys”• Reduces distance of finger stretches

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Specialty Keyboards

• Laptops

• PDAs

• Wireless

• Ergonomic

Laptop

Ergonomic

PDA

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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

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Inputting Sound• Microphone Input

– Teleconferencing– Voice over Internet– Voice Recognition

Microsoft Voice Recognition

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Input for the Physically Challenged

• Visually Impaired– Voice recognition– Keyboards with large keys– On-screen keyboards

• Motor control – Special trackballs– Head-mounted devices

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Other Input Devices• Scanners

– Text (OCR)– Images – Bar codes– RFID tags

• Digital cameras– Images – Video

Flatbed

Handheld

Camera Camcorder

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Output Devices

• Retrieving information from the computer's memory for human use

• Output devices – Softcopy (video,

sounds, control signals)

– Hardcopy (print)

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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

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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

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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

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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

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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.

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Dot-matrix

Printers

Inkjet

Multifunction

Laser

Plotter

Thermal printer

• Impact printers– Dot-matrix

• Nonimpact printers– Inkjet– Laser – Multifunction

• Specialty printers– Plotters– Thermal printers

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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

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Comparing Printers

• Speed - ppm

• Resolution - dpi

• Color / BW

• Memory - MB

• Cost of device

• Cost per page - ink or toner

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Outputting Sound

• Voice synthesis– Stephen Hawking

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Outputting Sound

• Speakers and Headphones

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The System Unit

Box that contains the central electronic components of the computer:– CPU/RAM/

motherboard– Expansion cards– Power supply– Storage devices

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The Front Panel• Drive bays• Memory card

reader• Floppy drive• Productivity

ports• Power button

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The Back

• Ports for peripheral devices

• Types of ports:– Serial– Parallel– VGA– USB– Connectivity

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Inside the System Unit

• Essential electronic components used to process data

• Types of components:– Power supply– Secondary storage– Motherboard– CPU– Expansion cards

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The Motherboard

• CPU (chips)

• RAM

• Expansion cards

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Expansion Cards

• Adds functions

• Provides new connections for peripheral devices

• Common types:– Sound– Modem– Video (VGA)– Network (NIC)

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Secondary StorageHard 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!)

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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

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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"

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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."