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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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