How Computers Work

1
Chapter 1

• How Computers Work

2
You Will Learn

• About the functions performed by different
  hardware components of a microcomputer
• About the three kinds of software and how they
  relate to one another and to hardware
• How the CPU uses primary and secondary storage to
  manage software

3
Hardware and Software

• Hardware
• Physical components of the computer
• Monitor
• Keyboard
• Memory chips
• Hard drive
• Software
• Set of instructions that directs the hardware to
  accomplish a task

4
Chauffer Analogy
5
Functions of Hardware
6
Binary Number System
7
Hardware

• Central processing unit
• Most important hardware device
• Receives input and sends output
• Stores data and instructions performs
  calculations
• Requirements of hardware devices
• Method for CPU to communicate with the device
• Software to instruct and control the device
• Electricity to power the device

8
Hardware Used for Input and Output

• Ports
• Physical connectors that allow a cable from a
  peripheral device to be attached
• Input devices
• Keyboard
• Mouse
• 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 Computer Case

• System board
• Permanent storage
• Floppy drive
• Hard drive
• CD-ROM drive
• Power supply
• Circuit boards
• CMOS (most CPUs)
• TTL
• Cables

13
Hardware Inside the Computer Case
14
CMOS Chips

• Require less electricity
• Hold data longer after electricity is turned off
• Are slower
• Produce less heat

15
The System Board

• Largest and most important circuit board
• Contains the CPU

16
The System Board
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Major Components of System Boards

• For processing
• CPU
• Chip set that supports CPU by controlling many
  system board activities
• For temporary storage
• RAM
• Cache memory

continued
18
Major Components of System Boards

• Allow CPU to communicate with other devices
• BUS
• Expansion slots
• Firmware and setup information
• Flash BIOS memory chip
• CMOS configuration chip
• Electrical system
• Power supply connections

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Components Used Primarily for Processing

• CPU or microprocessor
• Executes most computer processes
• Chip set
• Relieves CPU of some processing
• Provides careful timing of activities to increase
  overall speed
• Coprocessor
• Supports and enhances function of some older CPUs
  (pre-1995)

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The CPU
21
Temporary (Primary) Storage Devices

• Used by the CPU to process data and instructions
• Provided by RAM (random access memory devices)
• SIMMS (single inline memory modules)
• DIMMS (dual inline memory modules)
• Cache memory

22
SIMMS and DIMMS
23
Cache Memory
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Permanent (Secondary) Storage Devices

• Remote to the CPU
• Permanently hold data, even when PC is turned off
• Most popular devices
• Hard disks
• Floppy disks
• Zip drives
• CD-ROMs

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Hard Drives
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Hard Drives
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Floppy Drives
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System Board Components Used for Communication
Among Devices

• Bus
• System clock
• Expansion slots
• PCI Used for high-speed input/output devices
• AGP Used for a video card
• ISA Used by older and/or slower devices

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Bus Lines
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System Clock
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Expansion Slots
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Expansion Slots
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Interface (Expansion) Cards

• Circuit boards inserted into a slot on the system
  board to enhance capability of the computer
• Common types
• Video card
• Network card
• Internal modem
• I/O controller card
• Network card

34
Video Card
35
The Electrical System

• Power supply
• Supplies power to the system board and other
  installed devices
• Provides 3.3, 5, and 12 volts DC

36
The Electrical System
37
The Electrical System
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The Electrical System
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Instructions and Data Stored on the System Board

• ROM chips
• Contain permanent programming code
• Sometimes called BIOS chips
• CMOS configuration chips
• Hold configuration or setup information
• Jumpers or DIP switches
• Hold configuration information

40
ROM BIOS Chip on a Video Expansion Card
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ROM BIOS Chip on the System Board
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CMOS Configuration Chip
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Jumpers
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Software

• The intelligence of the computer
• Computer programs, or instructions to perform a
  specific task
• Determines what hardware is present
• Decides how hardware is configured and utilized
• Uses hardware to perform tasks

45
Three Types of Software and What They Do

• Firmware (BIOS)
• Controls computers input/output functions
• Operating systems (OSs)
• Provide instructions to hardware to perform tasks
• Applications software

46
Functions of BIOS and OS
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Firmware or BIOS

• Provides basic instructions to hardware
• Often serves as the interface between
  higher-level software and hardware

48
Software Layers

• A hierarchy determines how software interfaces so
  that high-level software can depend on low-level
  software to manage the hardware for it
• Applications software depends on the OS to
  interface with hardware
• Instructs hardware directly
• Uses BIOS to provide the instructions
• Uses device drivers

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Software Layers
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How Software Manages and Shares Information
51
Operating Systems

• Different OSs are written to support different
  types of hardware systems and user needs

52
Functions of Operating Systems

• Manage BIOS
• Manage files on secondary storage devices
• Manage primary memory (RAM)
• Diagnose software and hardware problems
• Interface between hardware and software
• Perform housekeeping procedures requested by user

53
Starting Up the Operating System

• OS programs must be copied from secondary storage
  into RAM (memory)
• CPU then reads from one memory location in RAM to
  another to receive and follow instructions

54
Starting Up the Operating System
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Interfacing with the Operating System

• Command-driven interface
• Menu-driven interface
• Icon-driven interface (graphical user interface
  or GUI)

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Command-driven Interface
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Menu-driven Interface
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Icon-driven Interface
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Icon-driven Interface
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Survey of Operating Systems

• Terms
• Multitasking
• Cooperative multitasking (task switching)
• Preemptive multitasking
• Windows 3.x operating environment

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Multitasking Environment
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Windows 3.x Operating Environment
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Well-known Operating Systems

• DOS (disk operating system)
• DOS with Windows 3.1 and 3.11 operating
  environments
• Windows 95 and Windows 98
• UNIX operating system
• Windows NT
• OS/2
• Macintosh operating system

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Disk Operating System (DOS)
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DOS with Windows 3.x
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Windows 9.x
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UNIX
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Windows NT
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OS/2
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Macintosh Operating System
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How an Operating System Manages an Application

• DOS naming conventions
• Filename (up to 8 characters)
• File extension (3 characters)
• Memory addressing under DOS

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Operating System Modes

• Real mode
• Single-tasking operating mode whereby programs
• Only have 1024K of memory addresses
• Have direct access to RAM
• Use a 16-bit data path
• Protected mode
• Supports multitasking whereby
• The OS manages memory
• Programs have more than 1024K of memory addresses
• Programs can use a 32-bit data path

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Real Mode
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Protected Mode
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Applications Software

• Eight categories word processing, spreadsheet,
  database management, graphics, communications,
  games, mathematical modeling, and software
  development tools
• Designed to work on top of a particular OS
• Comes written on floppy disks or CD-ROMs usually
  must be installed on a hard drive in order to run

76
How Applications Software is Loaded and
Initialized

• OS receives command to execute application
• OS locates program file for the application
• OS loads program file into memory
• OS gives control to the program
• Program requests memory addresses from OS for its
  data
• Program initializes itself may request that data
  from secondary storage be loaded into memory
• Program turns to user for its first instruction

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How Applications Software is Loaded and
Initialized
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How Applications Software is Loaded and
Initialized
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Launching a Program File
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Copying the Program into Memory
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Loading Applications Software Using Windows 3.x
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Loading Applications Software Using Windows 3.x
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Loading Applications Software Using Windows 3.x
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Loading Application Software Using Windows 9x

• Place shortcut icon directly on desktop
• Click Start button, select Programs, select
  program from list of installed software
• Use Run command, after clicking Start button on
  the taskbar

85
Applications Software Summary

• Applications software is executed by either the
  operating environment (Windows 3.x) or the OS
  software 9 (DOS or Windows 9x)
• When an application is executing, you are
  interacting with the application
• Applications software interacts with OS software
  that is executing it
• OS software interacts with hardware
• OS software might interact with the hardware
  through BIOS or the device driver

86
Chapter Summary

• Individual components that make up a computer
  system hardware and software
• Hardware
• Devices used for input, output, processing, and
  storage of data
• Components that make up the electrical system
• Components used for communicating data and
  instructions from one device to another
• Importance of buses on the system board

continued
87
Chapter Summary

• CPU
• Central processing point for all data and
  instructions
• Both data and instructions must be stored in
  memory with assigned memory addresses before
  processing can begin

continued
88
Chapter Summary

• Software
• Works in layers
• Lowest layer (BIOS and device drivers) interfaces
  with hardware
• Highest layer (applications software) interfaces
  with user
• OS is the middleman layer coordinating everything