Information System Hardware

1
Chapter 4

• Information System Hardware

2
What is a computer

• A computer is a device that is
• Electronic
• Can store data
• Can store and follow a set of software
  instructions, called a program.

3
Input Devices

• An input device accepts data from outside the
  computer and converts it into an electronic form
  the computer can understand.
• Keyboard
• Pointing devices
• Scanner
• Touch screen
• Light pen/electronical pen/stylus (pen like
  instrument)
• Pen commuter (these input devices use pen
  technology)
• Digitizer (digitizing) tablet/graphics tablet
  (this instrument is used in computer aided
  design/CAD)
• Personal digital assistant (PDA)

4
Output Devices

• An output device converts data from an electronic
  form inside the computer to a form that can be
  used outside the computer.
• Monitor (is a device that produces on screen
  text, graphics, images)
• Printer (is an instrument that produces on paper
  text graphics, images)
• Plotter (is an instrument that produces on paper
  high quality graphic output)

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Primary Storage

• Primary storage, read and write storage, also
  called internal storage, is the memory, or RAM,
  of the computer.
• Primary storage, which is temporary storage, is
  dependent upon continuous electrical power. Any
  interruption of electrical power causes the
  contents of primary storage to be lost.

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Central Processing Unit (CPU)

• The CPU, or processor, carries out the
  instructions of the program. It contains
  circuits that control the operations of the
  hardware an the circuitry that performs
  arithmetic and logical operations.
• Data is transferred from primary storage to the
  CPU with the results sent back to primary
  storage.

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Secondary Storage

• Secondary storage, also called auxiliary storage,
  stores data not currently being processed by the
  computer and represents permanent storage.
• Data is usually transferred to and from Secondary
  storage.
• Examples include hard disks, floppy disks, ZIP
  disks, CDROMs, and DVDs.

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Keyboards

• Most widely used input device.
• Possible physical problems include
• Repetitive strain injuries
• Carpal tunnel syndrome
• Ergonomically designed keyboards may improve user
  comfort and efficiency and reduce risk of injury.

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Pointing Devices

• Mouse
• Trackball
• Track point/pointing stick
• Track pad/touch pad
• Cursor (is an on screen symbol that shows the
  current position of the pointing device)

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Other input devices

• Touch screen
• Light pen/electronic pen that are used with
  Graphics tablet/Digitizer tablet

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Optical Scanning Input Devices

• Bar-code scanner
• Universal Product Code (UPC)
• Flat bed, or page scanner
• Automatic document feeder (ADF) scanner
• Mark-sense readers

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Magnetic Scanning Input Devices

• Magnetic strip reader
• Credit cards
• ID Cards
• Magnetic Ink Character Recognition (MICR) used
  at the bottom of all checks by the banking
  industry.

13
Voice Input Devices

• Uses a microphone connected to the computer and
  translates the spoken word to digital input.

14
Video Input Devices

• Digital cameras that converts photographic images
  in to digital format.

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Screens, Monitor, or CRT

• Key elements of a screen include
• Pixels picture elements arranged as a pattern
  of dots.
• Screen resolution the number of pixels that can
  be displayed on a screen at one time.
• Refresh rate the number of times per second
  that screen repaints itself.

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Screens, or Monitor, or CRT (contd.)

• Types of monitors
• Traditional tube monitors, or cathode
  (electronic gun) ray tube (CRT).
• Flat-panel screens most common type is liquid
  crystal display (LCD).
• Screen projector used to display a computers
  output on a large screen.

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Printers

• Printer classifications
• Impact printer
• Nonimpact printer
• Serial printers
• Line printers
• Page printers
• Letter-quality printers
• Draft-quality printers

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Desktop printers

• Ink-jet, or bubble-jet printer
• Typically 200 to 300 characters per second
• Laser printers
• Typically between 4 and 24 pages per minute.
• Dot matrix printer
• Typically between 200 and 300 characters per
  second.

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High volume printers

• Line printers
• High end line printers can print as much as 3,600
  lines per minute (at 60 lines per page, that is
  60 page per minute) and can cost 50,000.
• Page printers
• High end page printers can print as much as 200
  pages per minute and can cost 100,000.

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Other Output Devices

• Plotters
• Voice output devices converting digitized data
  into synthesized speech
• Specialized devices for people with disabilities
  can include large typeface screens, Braille
  display devices.

21
Virtual Reality

• Virtual reality is the use of a computer to
  produce realistic images and sounds in such a way
  that the user senses that he or she is a part of
  the scene.
• Applications include architectural design, home
  remodeling, aircraft design, machine design, and
  more.

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Primary Storage Structure

• Input data is stored in primary storage (memory)
  after it is received from an input device.
• Output data is stored in primary storage before
  it is sent to an output device.
• Without sufficient primary storage, it may not be
  possible to execute certain programs or use
  certain data.

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Primary Storage Structure (contd.)

• Silicon chips integrated circuits
• Volatile storage dependent upon continuous
  power
• Random Access Memory (RAM)
• Non-volatile storage
• Read-Only Memory (ROM)

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Primary Storage Structure (contd.)

• Binary representation
• A combination of positive and negative electrical
  charges, represented by 1s and 0s when written to
  represent a character.
• One charge is called a bit.
• Eight bits are required to represent a single
  character, called a byte.
• The 256 possible (28) binary combinations are
  defined in character set.

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Primary Storage Structure (contd.)

• Personal computer character set
• ASCII American Standard Code for Information
  Interchange
• Mainframe computer character set
• EBCDIC Extended Binary Coded Decimal
  Interchange Code
• Though each contains 256 characters, the
  definitions are not the same, so a translator
  is required for one machine type to talk with
  the other machine type.

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Primary Storage Structure (contd.)

• Storage capacities
• Kilobyte (KB) or 1024 bytes (210) approximately
  1,000 bytes, thus the kilo
• Megabyte (MB) or 1,048,756 bytes (220)
• Gigabyte (GB) or 1,073,741,824 bytes (230)
• Terabyte (TB) or 1,099,511,627,776 bytes (240)

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Two Main Parts of a CPU

• Arithmetic-Logic Unit (ALU)
• May add, subtract, multiply and divide two
  numbers. More complex operations are are
  completed by using sequences of the four basic
  operations.
• Control Unit
• Analyzes and executes instructions in a program.
  Instructions are brought in one at a time from
  primary storage.

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CPU Speed

• Early CPUs processed 8 or 16 bits at a time.
• Current CPUs process 32 bits, and some can
  process 64 or 128 bits at a time.
• The roadway from primary storage to the CPU is
  the bus. Higher bus capacities mean faster
  computers.

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CPU Speed (contd.)

• Clock speed
• Measured in megahertz (MHz) or gigahertz (GHz).
• One MHz is one million cycles per second.
• One GHz is one billion cycles per second.
• Earliest IBM PCs ran at 4.77 MHz.
• Current PCs run at or above 2,000 MHz (2 GHz).

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Types of Secondary Storage

• Magnetic Disk Storage
• Floppy disk
• Hard disk
• ZIP disk

• Disk organization
• Disk
• Head (or side)
• Track
• Cylinder

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Optical Disk Storage

• Compact disks (CDROMs)
• Writable Compact Disks (CD-RWs)
• Digital Video Disks or Digital Versatile Disks
  (DVDs)

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Magnetic Tape Storage

• Data transferred to the tape via a magnetic tape
  drive.
• Data on a tape can only be read sequentially.