Input and Output

1
Input and Output

• Lecture 6

2
Competencies

• Explain the difference between keyboard and
  direct-entry input devices.
• Describe the features of keyboards and the four
  types of terminals.
• Describe direct-entry devices used with
  microcomputers.

3
Competencies

• Discuss voice recognition systems.
• Describe monitors and monitor standards.
• Describe printers and plotters.
• Describe voice-output devices.

4
Input devices

• Input devices are hardware devices that convert
  people-readable data into machine-readable form
  (translate human language to machine language).
• The computer can only understand machine
  language, which is represented by a binary system
• Machine language is machine-readable electronic
  signals of 0s and 1s.

5
Data Entry

• Keyboard entry
• Direct entry

6
Data Entry

• Point-of-sale (POS) terminal
• keyboard
• bar scanning
• Wand reader (scanner)

A Point-of-sale transaction
7
Bar Codes

• http//www.barcode-1.com
• Several standards (UPC/EAN common)
• guard bars lead in
• Bars, gaps 1,2,3 or 4 units wide
• Each digit 7 units in all
• Direction of scan and coding of 1 and 0
  switches at midpoint ensures code can be read
  unambiguously in either direction
• Example is ISBN starts 978, next digit(s)
  language, then publisher then title. Last digit
  is checksum.

8
Traditional keyboard
Numeric keypad
Function keys
Escape key
Navigation keys
Spacebar
9
Keyboard Entry

• Ctrl, Alt and Shift keys

10
Keyboard Entry

• A keyboard can be connected to a computer system
  through a terminal.
• A terminal is a form of input and output device.
• A terminal can connect to a mainframe or other
  type of computers called a host computer or
  server.

11
Keyboard Entry

• Terminals
• Dumb terminal
• Intelligent terminal
• Network terminal
• Internet terminal

12
Dumb Terminal

• Used to input and receive data only.
• It cannot process data independently.
• Example a terminal used by an airline
  reservation clerk to access a mainframe computer
  for flight information.

13
Intelligent Terminal

• Includes a processing unit, memory, and secondary
  storage.
• It uses communications software and a telephone
  hookup or other communications link.
• Example A microcomputer connected to a larger
  computer by a modem or network link.

14
Network Terminal

• Also known as a thin client or network computer.
  
• It is a low cost alternative to an intelligent
  terminal.
• Most network terminals do not have a hard drive.
  
• This type of terminal relies on a host computer
  or server for application or system software.
• Example our computer laboratory

15
Internet Terminal

• Is also known as a web terminal.
• It provides access to the Internet and displays
  web pages on a standard television set.
• It is used almost exclusively in the home.

16
Direct entry

• creates machine-readable data that can go
  directly to the CPU
• reduces human errors that may occur during
  keyboard entry
• includes pointing, scanning, and voice-input
  devices

17
Pointing Devices

• Mouse
• Trackball (rotating a ball with your thumb)
• Touch-surface (moving and tapping your finger on
  the surface of a pad)
• Touch screen (special kind of monitor screen
  covered with a plastic layer)

18
Pointing Devices

• Light pen
• Digitizer
• Digital camera
• Digital notebook

19
Pen-based computer recording inventory
20
Scanning Devices

• Image scanner (converts images to electronic
  signals)
• Fax machine
• Bar-code reader (reads vertical striped marks )

21
Scanners

• For text and graphics
• Quality depends on glass area, colour depth
  (accuracy), features (e.g. ability to scan
  transparencies) and dots-per-inch resolution
  (dpi) up to about 1200 dpi
• Film scanner resolution (2880 dpi typical, more
  for bureau machines), speed, features (e.g.
  scratch recovery)

22
After scanning recognition

• Magnetic-ink character recognition (MICR) reads
  numbers on the bottom of checks
• Optical-character recognition (OCR) reads
  preprinted characters
• Optical-mark recognition (OMR) reads presence or
  absence of marks on tests

23
Fax Machines

• Fax machine
• Fax modem cards

24
Bar-Code Readers

• Photoelectric scanners
• Bar code

25
Digital cameras

• Characteristics (mega)pixels, resolution, no. of
  stored images, speed of download. Other
  parameters as per analogue cameras.
• Clever compression algorithms needed to store and
  transmit video still produce large files.
• High compression requires a lot of processing

26
Voice-Input Devices

• Convert speech into digital code
• Microphone
• Voice recognition systems (microphone, sound
  card, and software)

27
Voice Recognition Systems

• can be used to operate microcomputers or create
  documents
• must be trained to the particular users voice
• Two types
• Discrete Speech directly converts the spoken
  word into printed material
• Continuous Speech able to accept dictation as
  well as spoken commands used to issue commands
  to special applications

28
Output

• Monitors, printers, plotters and voice

29
Output

• Output is people-readable information.
• INPUT ? PROCESSING ? INFORMATION
• Four output devices
• Monitors
• Printers
• Plotters
• Voice-output

30
Monitors

• The most frequently used output devices.
• Two important characteristics of a monitor are
• size and
• clarity.

31
Monitor size

• A monitors size is indicated by the diagonal
  length of its viewing area.
• Common sizes for monitors are 15, 17, 19, and 21
  inches.
• Larger monitors can display more information at
  one time.
• Larger monitors are more expensive.

32
Monitor Clarity

• A monitors clarity is indicated by its
  resolution.
• Resolution is measured in pixels.
• Pixels are individual dots of picture elements
  that form images on a monitor.
• The greater the resolution (more pixels), the
  better the clarity of the image.

33
Monitor Clarity

• Standard screen resolutions
• (640 x 480)
• 800 x 600
• 1024 x 768
• 1280 x 1024
• 1600 x 1200
• 1680 x 1050 (my laptop)

34
Monitor Standards

• Standards have been created to indicate a
  monitors color and resolution capabilities.
• SVGA
• XGA
• SXGA
• UXGA

35
SVGA

• Super Video Graphics Array
• Has a minimum resolution of 800 by 600 pixels.
• Primarily used with 15-inch monitors.

36
XGA

• Extended Graphic Array
• Has a resolution of 1024 by 768 pixels.
• Popular today with 17-inch and 19-inch monitors.

37
SXGA

• Super Extended Graphics Array
• Has a resolution of 1280 by 1024 pixels.
• Popular with 19-inch and 21-inch monitors.

38
UXGA

• Ultra Extended Graphics Array
• The newest and highest standard.
• Popularity expected to increase with 21-inch
  monitor use.
• Primarily used for high end engineering design
  and graphics arts.

39
Desktop Monitor The Cathode-Ray Tube (CRT)

• phosphors excited by electron gun beams
• RGB composite color
• horizontal scanning pattern to refresh phosphors

40
Portable Monitors

• Flat-Panel or LCD (Liquid crystal display)
• Passive-matrix or dual-scan
• Creates images by scanning the entire screen.
  Requires very little power. Clarity of image is
  not as sharp as active-matrix.
• Active-matrix
• Each pixel is independently activated to form
  images.
• More colors with better clarity can be displayed.
• Are more expensive and require more power.

41
Monitor - example

• 17" FST monitor, 0.28 mm, 12801024
• 17is the diagonal size of the tube visible part
  is usually rather less. FST Flatter Squarer
  Tube
• (0.28 mm is the dot pitch smaller is better)
• 12801024 is the screen resolution in
  pixelsAbout 43 aspect ratio (like a TV)

42
Note

• Output on a monitor is referred to as soft copy.
• Output on a printer or plotter is referred to as
  hard copy.

43
Printers

• Ink-jet Printer the most widely used.
• Laser Printer used in applications requiring
  high-quality output.
• Thermal Printer widely used to produce very
  high quality color artwork and text.

44
Printers

• Dot-matrix printer used to be the most widely
  used
• Chain printer - Expensive, high-speed machines

45
Ink-jet printers

• Sprays small droplets of ink at high speed onto
  the surface of the paper.
• Produces a letter-quality image.
• Permits printing in a variety of colors.
• Reliable, quiet, and inexpensive.

46
Laser Printers

• Uses a technology similar to that used in
  photocopying machines (laser beam).
• Produces images with excellent letter and
  graphics quality.
• More expensive than ink-jet printers.
• Personal inexpensive and used by many single
  users. (4-6 pages a minute)
• Shared more expensive and shared by a group of
  users. (over 30 pages a minute)

47
Thermal Printers

• Widely used to produce very high quality color
  artwork and text.
• Uses heat elements to produce images on
  heat-sensitive paper.
• Not as popular because of cost and requirement of
  specially treated paper.
• Produces near-photographic output.

48
Dot Matrix Printers

• Was once the most widely used microcomputer
  printer.
• Forms characters or images using a series of
  small pins on a print head.
• Are inexpensive and reliable, but noisy.
• Often used for draft documents or documents that
  will not be shown to customers.

49
Plotters

• Special-purpose output devices used to produce
  charts, maps, architectural drawings, and 3-D
  illustrations.
• They can produce high-quality multicolor
  documents or larger size documents.

50
Printers

• Speed measured in pages per minute (ppm) depends
  on material
• Quality resolution is measured as dots-per-inch
  (dpi)
• 600 dpi is typical,
• 1440 dpi for photo printers

51
Note relative quality

• Scanner 1200 dpi
• Printer 3-600 dpi photo printer 2880 dpi
• Monitor lt 100 dpi
• A scan at 1200 dpi contains (1200/100)2 144
  times the information of one at 100 dpi
• Not much point if just for viewing on a monitor
  (But what about viewing it in 10 years time?)
• Film scans 35 Mb need storage device.

52
Voice-Output Devices

• Make sounds that resemble human speech.
• Use prerecorded vocalized sounds to produce
  output. The computer speaks synthesized words.
• Example stereo speakers and headphones.
• Devices are connected to a sound card in the
  system unit.
• Sound card is used to capture sound as well as
  play it back.

53
Sound systems

• Quality some kinds of error acceptable noise
  and poor frequency response is OK, breakup is
  not.
• Sound is the limiting factor in videoconferencing
  Network latency (end-to-end delay) is the issue.
• Clever compression algorithms needed to store and
  transmit sound MP3.