Hardware: Input, Processing, and Output Devices

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Hardware Input, Processing, and Output Devices

• Chapter 3

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Chapter Topics

• Computer system components
• The power, speed, and capacity of processing and
  main memory devices.
• Access methods, capacity and portability of
  secondary storage devices.
• Input output devices
• The popular classes of computer systems

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Hardware Typical System
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Computer Hardware
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On the Motherboard
A motherboard
CPU
A RAM chip
A firewire card
Pins to attach to The motherboard
Expansion slots
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CPU
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CPU
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Machine Cycle
Instruction Cycle
Fetch
Decode
Execute
Write-back
Execution Cycle
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Machine Cycle Time Measures

• Microseconds (1 millionth)
• Nanoseconds (1 billionth)
• Picoseconds (1 trillionth)
• MIPS (Millions of Instructions Processed per
  Second)

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How fast is a Nanosecond?

• If one nanosecond is..
• One mile
• One person
• One minute
• One square mile

• Then one second is equivalent to
• 2000 trips to the moon and back
• Population of China and the U.S.
• 1900 years
• 17 times the land are of the world

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Data Bus
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Processing Characteristics

• Clock speed electronic pulses affecting machine
  cycle time
• Hertz one cycle (pulse) per second
• Megahertz (MHz) millions of cycles per second
• Microcode internal, predefined elementary
  operations in a CPU

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Microcode Instruction Sets

• Complex instruction set computing CPU contains
  many microcode instructions
• Reduced instruction set computing (RISC)
  Minimal set of microcode instructions
• Very Long Instruction Word (VLIW) Each microcode
  instruction is longer and does more.

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Multiprocessing

• More than one CPU is present
• Tasks are divided among CPUs in true parallel
  processing
• Parallel processing uses multiple processors to
  execute instructions in concert.

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Parallel Processing
Control CPU
Combined Results
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Physical Characteristics of the CPU

• Digital circuits on chips
• Electrical current flows through silicon
• Moores Law states that transistor density of
  chips will double every 18 months

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Memory Characteristics and Functions
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Memories
Random Access Memory (RAM)
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ROM Chip and BIOS

• ROM stands for Read Only Memory
• ROM is a non-volatile memory on a chip
• The ROM chip contains
• Basic input/output system BIOS
• The BIOS has the instructions necessary
• to start up your computer

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RAM

• RAM stands for Random Access Memory
• RAM is a volatile memory on a chip
• RAM chips store information in addresses
• that can be accessed directly and quickly

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Storage Media

• Storage devices retain data when power is
  switched off
• Storage devices are slower than memory devices
  like RAM

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Memory Versus Storage

• Memory
• A temporary holding place for data and
  instructions
• Consists of one or more chips on the motherboard
• Sometimes called primary storage
• Storage
• The media on which data, instructions, and
  information are kept, as well as the devices that
  record and retrieve these items
• Storage also called secondary storage, auxiliary
  storage, permanent storage, or mass storage
• Storage is nonvolatile

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Managing Memory
Remember the Machine Cycle?
Page is swapped in
Decoding and Execution
Page is swapped out
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Starting Up

• BIOS read
• from ROM

2. OS kernel, or supervisor program becomes memo
ry resident.
3. CPU reads and executes instructions
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• Storage Capacity

Storage Term
Number of bytes
Abbreviation

• The number of bytes (characters) a storage medium
  can hold
• Manufacturers use many terms to define the
  capacity of storage media

Kilobyte
KB
1 thousand
Megabyte
MB
1 million
1 billion
Gigabyte
GB
Terabyte
1 trillion
TB
Petabyte
PB
1 quadrillion
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Data Representation

• A computer circuit represents the 0 or the 1
  electronically by the presence or absence of an
  electronic charge.
• Binary Digit (Bit) Electronic State
• 1 On
• 0 Off
• Binary system two unique digits, 0 and 1
• Bit the smallest unit of data the computer can
  represent
• A byte a group of 8 bits represents a single
  character in the computer

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Bits and Bytes

• Byte
• Eight bits
• Kilobyte - 1 thousand bytes
• Megabyte - 1 million bytes
• Gigabyte - 1 billion bytes
• Terabyte - 1 trillion bytes

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Coding Schemes

• A byte provides enough different combinations of
  0s and 1s to represent 256 individual characters.
  
• A coding scheme the defined combinations of 0s
  and 1s that represent characters by patterns
• ASCII(The American Standard Code for Information
  Interchange)
• ASCII represents 0-9, upper and lower case A-Z,
  and English language punctuation in byte code
• EBCDIC (The Extended Binary Coded Decimal
  Interchange Code)
• Unicode

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Data Storage Hierarchy
DOG.. CAT. FOX.
File
Record
DOG, FOUR LEGS, TWO EARS
Field
DOG
Character (byte)
D O G
Bits
01000100 01001111 01000111
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Storage Modes

• Direct(Random) Access
• records can be retrieved in any order
• Faster (nanoseconds)
• Usually more expensive
• Sequential
• records must be retrieved in order
• Slower (milliseconds)
• Less expensive

The dog barked.
T H E D O G . .
Th
bar
d
og
k
ed
e
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Sequential access versus Direct access

• Direct access
• Method used for floppy disks, hard disks, and
  compact discs
• Also called random access
• You can locate a particular data item or file
  immediately, without having to move consecutively
  through items stored in front of the desired data
  item or file
• Faster
• Used as the primary method of storage

• Sequential access
• Method used for tape
• Reading and writing data consecutively
• You must forward or rewind the tape to a specific
  point to access a specific piece of data
• Much slower
• Utilized most often for long-term storage and
  backup

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Storage Technologies

• Magnetic
• Read/write head uses electrical impulses to
  create or interpret patterns of magnetic impulses
• Floppy disks
• Hard disks
• Tape
• Optical
• Laser beam creates or reads non-reflective pits
  and reflective land areas
• CDs
• DVDs

Ancient DecTape systems
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Disks
Read/Write Head
Sector
Cluster
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• Access time

Memory (RAM)

• The amount of time it takes the device to locate
  an item on a disk
• Defines the speed of a disk storage device

Hard Disk
Compact Disc
Floppy Disk
Tape
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CD-R CD-RW

• CD-R (compact disc-recordable)
• You write on the CD-R using a CD recorder or a
  CD-R drive and special software
• The CD-R drive can read and write both audio CDs
  and standard CD-ROMs
• You cannot erase the discs contents
• Most CD-ROM drives can read a CD-R

• CD-RW (compact disc-rewritable)
• An erasable disc you can write on multiple times
• You must have CD-RW software and a CD-RW drive

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DVD-ROM (digital video disc-ROM)

• An extremely high capacity compact disc capable
  of storing from 4.7 GB to 17 GB
• You must have a DVD-ROM drive or DVD player to
  read a DVD-ROM
• Looks just like a CD-ROM but data, instructions,
  and information is stored in a slightly different
  manner to achieve a higher storage capacity

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Magnetic Tapes

• A magnetically coated ribbon of plastic capable
  of storing large amounts of data and information
  at a low cost
• A tape drive reads from and writes data and
  information on a tape
• Older computers used reel-to-reel tape drives
• A tape cartridge is a small, rectangular, plastic
  housing for tape used in todays tape drives
• Used by business and home users to backup
  personal computer hard disks
• Both external and internal tape units for
  personal computers
• Larger computers use tape cartridges mounted in a
  separate cabinet called a tape library

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Storage techniques used in an enterprise system

• Storage area network (SAN) A high-speed network
  that connects storage devices
• Tape library A high-capacity tape system that
  works with multiple tape cartridges for storing
  backups of data, information, and instructions
• RAID system Ensures that data is not lost if one
  drive fails
• Server Stores data, information, and
  instructions need by users on the network
• CD-ROM jukebox Holds hundreds of CD-ROMs that
  can contain application programs and data. Also
  called a CD-ROM server
• Internet backup Stores data, information, and
  instructions on the Web

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RAID

• Redundant array of independent disks
• A type of hard disk system that connects several
  smaller disks into a single unit that acts like a
  single large hard disk
• More reliable than a traditional disk system but
  quite expensive
• RAID duplicates data, instructions, and
  information to improve data reliability

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• How does RAID work?

• Level 1, called mirroring, has one backup disk
  for each disk

• Levels beyond level 1 use a technique called
  striping, which splits data, instructions, and
  information across multiple disks in the array

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Additional Devices and Media

• Memory Cards
• A thin, credit card-sized device
• Fits into a PC Card slot on a notebook other
  personal computer
• Different types and sizes add storage, additional
  memory, communications, and sound capabilities to
  a computer
• Three types of PC Card
• Advantage of a PC Card for storage is portability
  between systems
• Flash memory
• Also called flash ROM or flash RAM
• Nonvolatile memory that can be erased
  electronically and reprogrammed
• Stores data and programs on many handheld
  computers and devices
• Flash memory cards store flash memory on
  removable devices instead of chips

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Input and Output
Device Driver software
Interrupts
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Input devices

• What is input?
• Any data or instructions you enter into the
  memory of the computer
• Users can input data and instructions in a
  variety of ways
• Types of input
• Data A collection of raw unprocessed facts,
  figures, and symbols
• Instructions Programs, Commands, User responses

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Data

• Data can be human or machine readable
• Data entry converts human readable data into
  machine-readable form
• Data input transfers machine-readable data into
  the system
• Source data automation

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Input Devices

• Personal computer input devices
• Keyboard
• Mouse
• Voice-recognition devices
• Digital cameras
• Terminals

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Input Devices

• Scanning devices
• Optical data readers
• Bar code scanners
• MICR devices
• POS (point-of-sale) devices
• Pen input devices
• Light pens
• Touch screens

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Output Devices

• Monitors
• Cathode Ray Tubes (CRTs)
• Liquid Crystal Displays (LCDs)
• Active matrix
• Passive matrix
• Printers
• Plotters
• Computer Output Microform (COM)
• Music Devices

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• What is a CRT monitor?

• Contains a cathode ray tube (CRT), a large
  sealed, glass screen
• The screen is coated with tiny dots of phosphor
  material
• A pixel, or picture element, is a single point in
  an electronic image
• Three dots (red, blue, and green) combine to make
  up each pixel

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• What is a liquid crystal display (LCD) monitor?

• A type of flat-panel display
• Uses liquid crystals between two sheets of
  material to present information on a screen
• An electric current passes through the crystals
  which creates the images on the screen

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• What is display resolution?

• Describes the sharpness and clearness of an image
• Resolution of a display device stated as dots, or
  pixels

Total of 480,000 pixels on screen
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• What is a video card?

• Converts digital output from the computer into an
  analog video signal
• Sends the signal through a cable to the monitor
• Controls how the display device produces the
  picture
• Also called a graphics card or video adapter

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How does video travel from the processor to a CRT
monitor?

• Step 1 The processor sends digital video data
  to the video card.

Step 2 The video cards digital-to-analog
converter (DAC) converts the digital video data
to an analog signal.
Step 3 The analog signal is sent through a cable
to the CRT monitor. Step 4 The CRT monitor
separates the analog signal into red, green, and
blue signals. Step 5 Electron guns fire the
three color signals to the front of the CRT. Step
6 An image displays on the screen when the
electrons hit phosphor dots on the back of the
screen.
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• What is bit depth?

• The number of bits a video card uses to store
  information about each pixel
• Also called the color depth
• Determines the number of colors a video card can
  display
• The greater the number of bits, the better the
  resulting image

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• What are various video standards?

• The Video Electronics Standards Association
  (VESA) develops video standards

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Computer System Types

• Network computer
• Personal computer
• Workstation
• Midrange computer
• Mainframe computer
• Supercomputer

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Selecting and Upgrading Computer Systems

• Computer system architecture the configuration
  of a computer systems hardware components