How Computers Work

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Chapter 1

• How Computers Work

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You Will Learn

• That a computer requires both hardware and
  software to work
• About hardware components inside and connected to
  a computer
• How the CPU works and how it communicates with
  other devices

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Hardware Needs Softwareto Work

• Hardware
• Physical components of the computer (monitor,
  keyboard, memory chips, hard drive)
• Software
• Set of instructions that directs hardware to
  accomplish a task

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Functions of the Microcomputer

• Input
• Processing
• Output
• Storage

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Communication Between Hardware and Software
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Binary Number System
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PC Hardware Components

• Input and output devices outside computer case
• Processing and storage components inside the
  case
• Hardware devices require three elements to
  operate
• Method for CPU to communicate with it
• Software to instruct and control it
• Electricity to power it

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Hardware Used forInput and Output

• Connects to computer case by ports
• Most popular input devices
• Keyboard
• Mouse
• Most popular output devices
• Monitor
• Printer

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Ports
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Input Devices
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Output Devices
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Hardware Inside the Case

• Motherboard (contains CPU, memory, etc.)
• A floppy drive, hard drive, and CD-ROM drive
  (permanent storage)
• Power supply with cords supplying electricity to
  all devices inside the case
• Cables connecting devices to circuit boards and
  the motherboard

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Hardware Inside the Case

• Circuit boards (used by CPU to communicate with
  devices inside/outside the case)
• Contain microchips manufactured in one of two
  ways
• As CMOS (complementary metal-oxide semiconductor)
  chips
• As TTL (transistor-transistor logic) chips

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The Motherboard

• Largest, most important circuit board in the
  computer
• Contains the CPU
• All communications between CPU and other devices
  must pass through the motherboard
• Also called the main board or system board

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The Motherboard
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Ports Provided by a Motherboard
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Major Components on All Motherboards

• For processing
• CPU
• Chip set that supports the CPU
• For temporary storage
• RAM
• Cache memory
• Electrical system
• Power supply connections

• For CPU communication with other devices
• Traces
• Expansion slots
• System clock
• Programming and setup data
• Flash ROM
• CMOS setup chip

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The CPU

• The microprocessor
• Performs most of actual data processing

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The Chip Set

• Controls flow of data and instructions to and
  from the CPU
• Provides careful timing of activities

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CPU and Chip Set Manufacturers

• IBM-compatible PCs
• Intel Corporation
• AMD
• VIA
• SiS
• Cyrix
• Macintosh (Apple Computer, Inc.)
• Motorola Corporation

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Storage Devices

• Temporary (primary storage, or memory)
• Temporarily holds data and instructions while
  processing them
• Faster to access than permanent storage
• Permanent (secondary storage)

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Primary and Secondary Storage
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Primary Storage Devices

• Memory, or RAM, located on the motherboard and on
  other circuit boards
• Volatile versus nonvolatile (or ROM) memory
• Common types of boards that hold memory chips
• SIMMs (single inline memory modules)
• DIMMs (dual inline memory modules)
• RIMMs (memory modules manufactured by Rambus,
  Inc.)

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RAM Chips
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Types of RAM Modules
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Secondary Storage Devices

• Hard disks
• Floppy disks
• Zip drives
• CD-ROMs

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Hard Drive

• Uses EIDE (Enhanced Integrated Drive Electronics)
  technology can accommodate up to four EIDE
  devices on one system
• IDE provides two connectors on a motherboard for
  two data cables

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Motherboard with Two IDE Connectors
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A Typical System
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Hard Drives Power Supply
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Floppy Drive
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Floppy Drive
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CD-ROM Drive
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Motherboard Components Used for Communication
Among Devices

• The bus
• System of pathways used for communication and the
  protocol and methods used for transmission
• Includes a data bus, address bus, and control bus
• Motherboard has several buses
• System bus
• PCI bus
• AGP bus
• ISA bus

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Bus Lines
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Data Bus
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System Clock

• Synchronizes activity on the motherboard
• Sends continuous pulses over the bus that are
  used by different components to control the pace
  of activity
• Frequency of activity is measured in MHz, or 1
  million cycles per second

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System Clock
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Bus Lines

• Lines of a bus, including data, instruction, and
  power lines, often extend to the expansion slots
• Types of expansion slots
• PCI (Peripheral Component Interconnect)
• For high-speed input/output devices)
• AGP (Accelerated Graphics Port)
• For a video card
• ISA (Industry Standard Architecture)
• Used by older and/or slower devices)

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Bus Lines
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Types of Expansion Slots
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Interface (Expansion) Cards

• Enable the CPU to connect to an external device
  or to a network

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Interface (Expansion) Cards
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Full View of a Video Card
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The Electrical System

• Power supply
• Most important component of computers electrical
  system
• Converts/reduces electricity to voltage the
  computer can handle
• Runs a fan directly from electrical output
  voltage to cool inside of computer case

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Electrical System
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Electrical System
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Instructions and Data Stored on the Motherboard

• ROM BIOS
• Holds software needed to start up PC and begin
  loading an OS
• Most are flash ROM
• CMOS chip
• Stores setup (configuration) information
• Setup information can also be set by means of
  jumpers and DIP (dual inline package) switches
• Powered by a battery on motherboard when power is
  off

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ROM BIOS Chip
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ROM BIOS Chip
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CMOS Chip
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Jumpers
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DIP Switches
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How a CPU Works and Communicates with Other
Devices

• Responsible for most processing
• Depends on chip set, system clock, and buses to
  move data to and from I/O devices, memory, and
  secondary storage
• Only two states on and off

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Components of a CPU

• Input/output (I/O) unit
• Manages data and instructions entering and
  leaving the CPU
• One or more arithmetic logic units (ALU)
• Does all comparisons and calculations
• Control unit
• Manages all activities inside CPU itself

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Components of a CPU
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How the CPU Works

• Registers hold data and instructions while it
  processes them
• Memory cache holds data and instructions just
  before they are processed
• Internal bus runs at different speed than
  external bus

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How the CPU Uses Memory

• CPU accesses memory by way of the data bus

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How CPU and Devices Use System Bus to Communicate

• System bus components
• Data bus
• Address Bus
• Control bus

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The Address Bus
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The Control Bus

• System clock control line
• Provides timing for motherboard components
• Interrupt request (IRQ) lines
• Used by devices to get CPUs attention assigned
  at setup
• Read/write control lines
• How to use address on address bus (read or write
  operation)
• I/O control lines
• How to use address lines (memory addresses or I/O
  addresses)

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Interrupt Request (IRQ) Lines
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I/O Control Lines
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Understanding Binary

• With computers, everything is binary every
  process is a series of zeros and ones
• Decimal and hexadecimal notations are two
  shorthand ways of displaying binary numbers

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Understanding Binary

• Hexadecimal notation (hex)
• Shorthand way to display long binary numbers
  easier for humans to understand
• Built on multiples of sixteen
• ASCII (American Standard Code for Information
  Interchange) standard
• Has assigned an 8-bit code for letters, symbols,
  and other characters

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Computer Terminology
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Chapter Summary

• Hardware needs software to work
• PC hardware components
• How a CPU works and communicates with other
  devices
• Understanding binary