Chapter 3 Interfaces Between You and the Computer Computer Components & Networks, 2002 Input/Output Hardware

Chapter 3

Interfaces Between You and the Computer

Computer Components & Networks, 2002

Input/Output Hardware

Ch 3 © Computer Components & Networks, 2002 2 CCI

Overview• I/O usage

• Input hardware

• Output hardware

• Combined input and output devices


Input Hardware

• Translate data into a form the computer can process.

• Three types: – keyboard – pointing – source-entry


Keyboard

• Standard keys– type characters– CAPS lock

• Cursor-movement keys– arrows, page up, page down

• Numeric keys– for calculating (Num Lock)

• Function keys– “F” keys, for software functions

• Special-purpose keys– Alt, Ctrl, Shift, Escape, Enter


Keyboard (Cont’)


Pointing Device

• Control the position of the cursor or pointer on the screen.– Mice, trackballs, joysticks, and touchpads– Light pens– Digitizing tablets– Pen-based systems


Mice

• Can be wireless controlled by infrared or radio signals

• Can have a programmable wheel

• Can have additional buttonsA video about mouse


Microsoft Mouse


Logitech Mouse


Joystick


Which point device is best?• Mouse

– Relatively inexpensive

– Little finger movement

– Foot print required is large

• Trackball– Uses less space

– Less movement than mouse

– Increased finger movement

• Touchpad– Less dust prone

– Less precision


Other Input• Light Pen

– light-sensitive stylus– use on display screens and ...

• Digitizing Tablets– for graphic design, computer animation, and

engineering diagramming

• Pen-based Systems– enter handwriting and marks into the

computer


Types of Pen-Based Systems• Gesture recognition or electronic checklists

• Handwriting stored as scribbling

• Handwriting converted to typed text– similar to voice-recognition, requires training

the software

• Handwriting, converted without training, to typed text– not that accurate at this point


PDAs

• Pen-based systems are most commonly used it in PDAs. Or Personal Digital Assistants, such as 3COM Palm III


Source-data Entry Devices

• Scanners, bar-code scanners, fax machines, imaging systems

• Voice-recognition devices

• Audio input devices

• Electronic cameras

• Sensors

• Human-biology input devices


Source-Data Entry• Does not require keystrokes

• Direct entry into computer often is more accurate

• Scanner devices– Bar-code readers– Mark and character recognition devices– FAX machines– Imaging systems


Bar-Code

• Vertical striped marks on most manufactured products

• Often seen is a Universal Product Code, as seen in North America and Australia


Other input devices• FAX machines

– facsimile transmission machine scans an image, then sends those electronic images over telephone lines

• Imaging systems– Image or graphic scanners convert

text, drawings, photographs into digital form which can then be transmitted elsewhere


Imaging Systems

• Used in Desktop Publishing

Multimedia Development

• Include scanners– External: flatbed, drum, or handheld– Internal: slide and photo


Scanner

德国 GiS公司所推出的Bookeye Planetray系列扫描仪


Voice Recognition System

• Using as microphone or telephone

• Converts to digital code

• Required a sound card

• Current technology up to 98%


Audio Input Devices

• Records or plays analog sound

• Translates for digital storage and processing


Audio Boards• Also called sound cards

• Some motherboards have built-in audio boards

• Three major standards– SoundBlaster– Ad Lib– Windows


Audio Board(2)


MIDI Boards

• Most support MIDI – musical instrument digital interface

• MIDI boards– used for multimedia applications


Video and Photographic Input• Most are analog

– frame-grabber video card– full-motion video card

• Digital video growing rapidly

• Advent of USB ports– rapid increase in digital cameras

• All-in-one cards– provide sound and video


Video Input

• Digital video– can be limited to the speed

of the computer and its ability to provide a consistent and high enough frames-per-second

– minimum to provide full-motion is 24 frames per second


Digital Cameras

• Use charge-coupled device (CCD)– light-sensitive photo cells

• Smallest 1/8th size of a 35 mm frame

• Up to 35 mm frame size• Approaching image

quality of 35mm


Digital Cameras(2)

A video about digit cameras


Input Controls

• Garbage in, garbage out

• Manual and computer-based controls

• Software often uses internal software tables to validate data input

• Reasonableness tests coded

• Care should be taken to ensure system is not too restrictive


Output Hardware

• What are the main characteristics of printers, plotters, multifunction devices, display screens, and audio output devices?


Printers

• Impact printers– Dot-maxtrix printer

• Non-impact printers– laser– ink-jet


Factors

• Resolution– The density of the gridwork of dots that create

an image– measured by the number of dots it can print per

linear inch, abbreviated as dpi

• Print speed– measured either by pages per minute(ppm) or

characters per second(cps)


Dot-matrix printer

• Impact printers– draft– near-letter quality– 40~300 cps– 72~144dpi

• An animation


Laser Printers• Use the same technology as a photocopier to

paint dots on a light-sensitive drum– Resolution: 300~1200dpi– Speed: 32~120 ppm for text only page

• Quit and fast• Black-and-white laser printers are popular

• A video


Ink-Jet Printers

• Slower, but less expensive than laser printers

• Bubble-jet variation– uses heat to force inks through print head

• Cartridges are often implemented in the following ways– single holder

• can often print color by switching cartridges


Printer Cartridge Variation

– double holder• can often print color

and photo quality by replacing cartridges

– quad holder• uses black, plus three

different color cartridges, or four color cartridges


Plotters

• Produce high-quality graphics, often on large formats

• Two basic types– ink-jet plotter

• slower, output on continuous drum

– electrostatic plotter• paper lies partially flat, similar to a photocopier

process


Printer or Plotter Installation

• Some drivers come preset within a BIOS

• Some come on included diskette or CD

• Often, more up-to-date drivers can be found from the manufacturer’s Web site

• Newer drivers than default drivers, such as keyboards or mice, may provide additional functionality


Multifunctional Printer Technology: All for One

• Often printing, scanning, copying, and faxing

• May not perform each function as quickly or as well as individual devices

• Statistically the repair record of these devices is equal to that of individual devices


Monitors

• The softcopy output

• Display adapters/video monitors have their own video chips and RAM

• CRTs– cathode ray tubes– also in television sets


Flat-Panel Screens

• Thinner, less weight

• Technologies used include:– Liquid crystal display (LCD)– Electroluminescent display (EL)– Active-matrix or dual-scan (passive-matrix)

using transistors


Screen Clarity

• Standard screen resolutions– 640 x 480– 800 x 600– 1024 x 768– 1280 x 1024– 1600 x 1200


Changing screen resolutions and refresh rates

• Consult manual for resolution and refresh rates prior to changing, as monitors may be damaged at ranges beyond capabilities


Dot Pitch & Refresh Rate

• Closer the pixels, the crisper the image

• Less than .31 mm provides clear viewing

• Multimedia and desktop publishing monitors often .25 mm pitch

• Refresh rate should be at least 72 Hz to avoid eye fatigue


Color

• Monochrome– black on white, white on black– amber on black– green on black

• Color monitors or RGB (red, green, blue)– between 16and 16.7 million color– based upon color depth


Monitor capacity and trade-off

• The more colors and the higher the refresh rate the harder the video card or adapter has to work

• The higher the color settings the slower the adapter

• The adapter and monitor must be compatible, including whether analog or digital


Audio Output Hardware

• Voice Output– Speech coding– Speech synthesis

• sounds called phonemes

• Sound Output– Digitized sounds – Beeps to music


Multimedia Output Needs• Sound or audio card

• Headphones

• Speakers


In & Out: Devices That Do Both

• Dumb terminals

• Intelligent terminals– processing capability but no storage

• Point-of-Sale (POS) Terminals

• Automated Teller Machines


Smart and Optical Cards

• Smart Cards– Credit-card like with

microprocessor

• Touch screens

• Future– retinal displays more

common

Documents

Chapter 3 Interfaces Between You and the Computer Computer Components & Networks, 2002 Input/Output Hardware