2002 prentice hall chapter 3 hardware basics: peripherals
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2002 Prentice Hall
Chapter 3
Hardware Basics: Peripherals
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Chapter Outline
Input: From Person to Processor
Output: From Pulses to People
Storage Devices: Input meets Output
Computer Systems: The Sum of Its Parts
“We swim in a sea of information.”Gary Snyder, poet
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Input: From Person to Processor
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The Keyboard
The most common input device is the keyboard, which is used to enter letters, numbers and special characters.
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Working with the Keyboard
• Function keys are special purpose keys whose function depends on the software being used.
• Cursor keys are used to move the cursor up, down, left, or right.
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Variations on Keyboard Design
Ergonomic to address repetitive stress injuries
Wireless
Folding
Half
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Pointing Devices
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Reading Tools
Optical-mark readers Bar-code readers Magnetic-ink character readers Wand readers Pen scanners
Input devices “read” directly from paper and convert printed information into bit patterns that can be processed by the computer.
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Digitizing the Real World
Scanner
Digital camera
Speech recognition
Sensing devices
Audio and video digitizers
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Scanners
Scanners capture and digitize printed images. There are several types of scanners:
Flatbed scanners
Handheld scanners
Sheet-fed scanners
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Digital Cameras
Digital cameras capture snapshots and store them as bit patterns on disks or other storage media.
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Video Digitizers
Video digitizers capture input from video sources such as video camera and convert it to a digital signal that can be stored in memory and displayed on a computer screen.
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Audio Digitizers
Audio digitizers capture spoken words, music and sound effects and convert them to digitized sounds.
These sounds can be stored in a computer’s memory and modified with computer software.
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Sensing Devices
Sensing devices are used to monitor temperature, humidity, pressure and other physical quantities.
The data collected provides data for use in robotics, environmental climate control, weather forecasting and other applications.
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Output: From Pulses to People
Screen Output
Paper Output
Sound Output
Controlling Other Machines
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Screen Output
A monitor or video display terminal (VDT) displays characters, graphics, photographic images, animation and video.
Video adapter—connects the monitor to the computer
VRAM or video memory—a special portion of RAM to hold video images (the more video memory, the more detail of a picture displayed)
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Screen Talk
Monitor size - measured as a diagonal line across the screen.
Pixels (or picture element) - tiny dots that compose a picture
Resolution - the number of pixels displayed on the screen (the higher the resolution, the closer together the dots)
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Image Quality
Image quality is affected by resolution and color depth (or bit depth)
Color depth refers to the number of different colors a monitor displays at the same time
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Examples of Color Depth
1-bit depth
16-bit depth8-bit depth
4-bit depth
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Monitor Classes
CRT (cathode ray tube) LCD (liquid crystal display)
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Cathode Ray Tube (CRT)
The cathode ray tube has the following characteristics:
Low cost Speedy response time Clear image
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Liquid Crystal Display (LCD)
Light-weight
Compact
Flat-panel
Used in overhead projection panels and video projectors to project computer images
More expensive than CRTs
Increasingly being seen with desktop computers
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Paper Output
Printers produce paper output or hard copy
2 kinds of printers: Impact printers Non-impact printers
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Impact Printers
Line printer Used by mainframes to
produce massive printouts Limited to printing characters
Dot matrix printer Images created by a matrix of
tiny dots Low print quality Low cost
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Non-impact Printers
A laser beam reflected off a rotating drum to create patterns of electrical charges
Faster and more expensive than dot matrix printer
High-resolution output
Laser Printer
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More on Non-impact Printers
Sprays ink onto paper to produce printed text and graphic images
Prints fewer pages/minute than laser printer
High-quality color costing less than laser printer
Ink-jet Printer
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Additional Output Devices
Multifunction peripheral or MFP combines a scanner, printer and a fax modem.
A plotter is an automated drawing tool that can produce large, finely scaled engineering blueprints and maps.
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Output You Can Hear
A sound card allows the PC to accept microphone input, play music and other sounds through speakers or headphones.
Synthesizers are included in sound cards and have specialized circuitry designed to generate sounds electronically.
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Controlling Other Machines
Robot arms Telephone switchboards Transportation devices Automated factory equipment Spacecraft Digiscents
Output devices take bit patterns and turn them into non-digital movements.
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Rules of Thumb: Ergonomics & Health
Choose equipment that’s ergonomically designed
Create a healthy workspace
Build flexibility into your work environment
Rest your eyes
Stretch to loosen tight muscles
Listen to your body
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Storage Devices: Input Meets Output
Secondary storage devices are computer peripherals capable of performing both input and output functions
Information is stored semi-permanently on tape and disk drives
Examples of storage devices Magnetic tapes and disks Zip, Jaz and SuperDisks Optical disks
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Magnetic Media
Magnetic tapes
Sequential access
Can store large amounts of information in a small space at a relatively low cost
Limitation: sequential access
Used mainly for backup purposes
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Magnetic Media
Magnetic drives Random access
Floppy disks for inexpensive, portable storage
Hard disks are non-removable, rigid disks that spin continuously and rapidly thus providing much faster access than a floppy disk.
Removable media (Zip & Jaz disks) provide high-capacity portable storage.
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Optical Media
Not as fast as magnetic hard disks Massive storage capacity and reliability
Optical disk drive uses laser beams to read and write bits of information on the disk surface.
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Types of Optical Media
CD-ROM drives are optical drives that read CD-ROMs.
CD-R are WORM media (write-once, read many).
CD-RW can read CD-ROMs and write, erase and rewrite data onto CD-R & CD-RW disks.
DVD (digital versatile disks) store & distribute all kinds of data. They hold between 3.8 and 17 gigabytes of information.
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Solid-state Storage Devices
Compact alternative
No moving parts
Designed for specific applications such as storing pictures in digital cameras
Likely to replace disk and tape storage
Flash memory is an erasable memory chip.
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Ports and Slots Revisited
The system or motherboard includes several standard ports:
Serial Port for attaching devices that send/receive messages one bit at a time (modems)
Parallel Port for attaching devices that send/receive bits in groups (printers)
Keyboard/Mouse Port for attaching a keyboard and a mouse
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More on Ports and Slots
Other ports are typically included on expansion boards rather than the system board:
Video Port used to plug in a color monitor into the video board
Microphone, speaker, headphone, MIDI ports used to attach sound equipment
SCSI port allows several peripherals to be strung together and attached to a single port
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Internal and External Drives
Hard drive
Bays
Hot swapping
CD or DVD
Floppy disk
Zip Drive
SCSI port
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Expansion Made Easy
USB (Universal Serial Bus) transmits a hundred times faster than a PC serial port
Firewire (IEEE 1394) can move data between devices at 400 or more megabits per second
– high speed makes it ideal for data-intensive work like digital video
With the open architecture of the PC and the introduction of new interfaces, you can hot swap devices.
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Putting It All Together with Networks
A typical computer system might have several different input, output, and storage peripherals. The key is compatibility.
Networks blur the boundaries between computers.
Networked computers may have access to all the peripherals on a system.
The computer is, in effect, just a tiny part of a global system of interconnected networks. b
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