Computing Components

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Session 2

• Computing Components

Nell Dale John Lewis
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Session Goals

• Begin to understand the jargon used in computing
• List the components and their function in a von
  Neumann machine
• Describe the fetch-decode-execute cycle of the
  von Neumann machine

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Session Goals (cont.)

• Describe how computer memory is organized and
  accessed
• Name and describe different auxiliary storage
  devices
• Define parallel computer configurations

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Computing as a Tool
Programmer / User
Applications Programmer (uses tools)
Systems Programmer (builds tools)
Domain-Specific Programs
User with No Computer Background
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Computing as a Discipline

• Four Necessary Skills
• Algorithmic Thinking
• Representation
• Programming
• Design

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Computer Components

• Consider the following ad

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Sizes in Perspective

• Admiral Grace Murray Hopper
• A coil of wire nearly 1,000 feet long
• Distance traveled by an electron along the wire
  in the space of a microsecond
• A short piece of wire
• In the space of a nanosecond
• A bag containing grains of pepper
• In the space of a picosecond

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Sizes in Perspective
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Stored-Program Concept
Figure 5.1 The von Neumann architecture
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System Components

• Hardware
• I/O devices (input/output)
• keyboard, mouse, monitor, etc.
• CPU
• Primary Storage
• Secondary Storage
• Software

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Typical System

• Computer case
• Monitor
• Printer
• Speakers
• Modem
• Keyboard
• Mouse

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Computer Components

• Power supply
• Hard drive
• Expansion card
• Expansion slot
• System board
• CD-ROM or DVD-ROM
• Floppy disk
• Drive bay
• Central Processing Unit (CPU)
• Random access memory (RAM)

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Processing
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The Fetch-Execute Cycle

• Fetch the next instruction
• Decode the instruction
• Get data if needed
• Execute the instruction

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The Fetch-Execute Cycle
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Sample Processing Sequence

• Two numbers in main memory are added
• Instruction is transferred from memory into the
  CPU
• Location of the instruction being processed is
  updated in the instruction counter (IC) or
  program counter (PC)
• The instruction just fetched is stored in the
  instruction register (IR)
• CU decodes the instruction to add two numbers
• operator operand1, operand2, operand3
• ADDW3 first_no, second_no, answer
• W words, 3 no of operands in the instruction
• Numbers are located in main memory
• Fetched into internal registers of the ALU by the
  CU
• Addition is carried out by ALU
• Sum stored in new memory location by CU
• The IC is updated to point to the next instruction

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Memory

• Memory is a collection of cells, each with a
  unique physical address

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Computer Architecture

• Microprocessor (examples Pentium, Pentium II,
  PowerPC, etc.)
• includes Bus Interface Unit, Arithmetic Logic
  Unit (ALU), Control Unit, registers
• motherboard is simply the main circuit board that
  contains most of these parts
• the CPU (central processing unit) is considered
  to be most of these parts taken as a whole
• Bus
• connects the microprocessor to the RAM ROM
• addresses for data and instructions are important

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CPU (Central Processing Unit)

• Processes instructions, performs calculations,
  and manages the flow of information
• Performance
• CPU speed is a major factor in determining how
  fast a computer operates (faster the speed,
  faster computer operates)
• Measured in gigahertz (GHz) A clock cycle relates
  to the clock that controls the timing in the
  microprocessor.
• For example, a 1.4GHz (gigahertz) clocked
  microprocessor generates 1.4 billion clock cycles
  per second.
• Each generation of CPU is more powerful than the
  one before. It's clock cycles are faster at a
  given speed

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Processing

• The Central Processing Unit (CPU) is the main
  chip in a computer
• Processes instructions
• Performs calculations
• Manages the flow of information

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Types of CPUs (Chips)

• Intel Pentium Processor
• Intel Celeron
• Needs of home machines
• AMD Athlon Processor
• Business and home use
• AMD Duron Processor
• Home use
• VIA Cyrix Processor
• Inexpensive CPU

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Main Memory / Primary Storage

• Speeds up computer by storing data the computer
  has recently used
• Internal Cache On CPU chip (L1 or primary cache
• External Cache On the system board and consists
  of Static RAM (SRAM chips)
• Sometimes built into chip
• RAM slower main memory
• Each time the computer requests data from RAM,
  the computer places a copy of the data in memory
  cache
• Constantly contains the most recently used data

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Storage Devices

• Primary storage
• RAM (Random Access Memory, or just memory for
  short)
• active data that is being stored, lost if power
  is cut off so save often
• ROM (Read-Only Memory)
• commands that are permanently stored on chips
• PCs use BIOS, Macs use the Toolbox
• Secondary storage
• Hard disk, floppy disks
• Slower method of storage retrieval but safer

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Random Access Memory

• Random Access Memory Temporarily stores data
  inside a computer
• Constantly overwritten
• Measured in megabytes (MB)
• If you have limited memory or you have many
  programs open, your computer may need to use part
  of the hard drive to simulate more memory

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RAM and ROM

• RAM stands for Random Access Memory
• Inherent in the idea of being able to access each
  location is the ability to change the contents of
  each location
• ROM stands for Read Only Memory
• The contents in locations in ROM cannot be
  changed
• RAM is volatile, ROM is not
• This means that RAM does not retain its bit
  configuration when the power is turned off, but
  ROM does

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Using Memory

1. Look through documents on your desk (internal
   cache)
2. Look through documents in your desk drawer
   (external cache)
3. Looking through documents in your filing cabinet
   (RAM)
4. Go out and get it from the trunk of your car
   (secondary storage)

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Control Unit

• Control unit is the organizing force in the
  computer
• There are two registers in the control unit
• The instruction register (IR) contains the
  instruction that is being executed
• The program counter (PC) contains the address of
  the next instruction to be executed
• ALU and the control unit called the Central
  Processing Unit, or CPU

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Arithmetic/Logic Unit

• Performing basic arithmetic operations such as
  adding
• Performing logical operations such as AND, OR,
  and NOT
• Most modern ALUs have a small amount of special
  storage units called registers

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Input/Output Units

• An input unit is a device through which data and
  programs from the outside world are entered into
  the computer
• Keyboard, the mouse, and scanning devices
• An output unit is a device through which results
  stored in the computer memory are made available
  to the outside world
• Printers and video display terminals

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Math Coprocessors

• A special processing unit that assists the CPU in
  performing certain operations.
• A math coprocessor is a chip or part of a chip
  that specializes in doing math. Hardware that
  attaches to the motherboard or is part of the
  CPU.
• Also called numeric coprocessors or floating
  point units (FPU).

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Flow of Information

• The parts are connected to one another by a
  collection of wires called a bus

Figure 5.2 Data flow through a von Neumann
architecture
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Bus

• Electronic pathway that carries information
  between devices in a computer
• Bus Width (think lanes of a highway)
• 8 bits is one character
• Bus Speed (think speed limit)
• Measured in MHz (millions of cycles per second)

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Parallel Processing
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Synchronous processing

• One approach to parallelism is to have multiple
  processors apply the same program to multiple
  data sets

Figure 5.6 Processors in a synchronous computing
environment
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Pipelining

• Arranges processors in tandem, where each
  processor contributes one part to an overall
  computation

Figure 5.7 Processors in a pipeline
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Peripherals
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Ports

• Ports are connectors at the back of a computer
  system that you use to plug in an external
  device. This allow instructions and data to flow
  between the computer and the device

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Any Port in a Storm

• Parallel port 25 holes female connector LPT1
  printer or storage devices
• Monitor port
• Keyboard port
• Serial port 9 or 25 pins male connector COM1
  mouse or modem
• Game port
• Network port
• USB port
• 127 devices
• Printer, modem, joy stick
• Firewire

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USB and Firewire

• High-speed ports that allow information to
  quickly transfer between a computer and an
  external device
• USB
• Supports up to 127 device
• USB 1.0 12 megabits per second
• USB 2.0 480 Mbps
• FIREWIRE
• 63 devices at 400 Mbps
• Can purchase Firewire expansion card

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Storage Devices
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Secondary Storage Devices

• Because most of main memory is volatile and
  limited, it is essential that there be other
  types of storage devices where programs and data
  can be stored when they are no longer being
  processed
• Secondary storage devices can be installed within
  the computer box at the factory or added later as
  needed

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Magnetic Disks

• A read/write head travels across a spinning
  magnetic disk, retrieving or recording data

Figure 5.5 The organization of a magnetic disk
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Hard Drives

• Magnetically stores data on rotating disks called
  platters
• Capacity is measured in bytes
• Speed is measured in revolutions per minute

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Floppy Drives and Drives

• Removable media
• Can be write-protected
• Can be damaged magnetically

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Magnetic Tape

• The first truly mass auxiliary storage device was
  the magnetic tape drive

Figure 5.4 A magnetic tape
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Tape Drive

• Backup helps you copy files to tape cartridges
• Try to find a drive that can store the entire
  contents of your hard drive

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Removable Storage Devices

• Jazz Drive 2 GB
• Zip Drive 250 MB
• LS-120 Drive 120 MB

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Compact Disks

• A CD drive uses a laser to read information
  stored optically on a plastic disk
• CD-ROM is Read-Only Memory
• DVD stands for Digital Versatile Disk

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CD-ROM

• ROM (Read-only memory) - cant be changed
• 650 Mb of data
• Equal to entire set of encyclopedias
• 400 Floppy disks
• Speed determines how fast a disk spins
• Look for 48X
• Speed of CD-ROM drive is the transfer rate
• In Kb (e.g. 3600Kbs)

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CD-R CD-RW Drives

• CD-R (Compact Disc Recordable)
• Permanent store not erasable
• CD-RW
• Can be erased and rewritten
• Read / Write and Re-write speeds
• Usually 74 minutes
• Special software needed to record onto a disk
• Referred to as burning a CD

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DVD-ROM Drive

• DVD Digital Versatile Disk
• Generally cannot change the information stored on
  a disk
• Similar to CD but stores more information
• Speed determines transfer rate (6 X)
• Capacity
• 1 side / 1 layer 4.7 GB
• 1 side / 2 layer 8.5 GB
• 2 sides / 1 layer 9.4 GB
• 2 sides / 2 layers 17 GB

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Input and Output
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Input Devices

• Keyboards
• Mice
• Trackballs
• Pointing Devices

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Scanners

• A scanner is a device that reads images and text
  into a computer
• Optical Character Recognition (OCR) software that
  places scanned text into a document that can be
  edited in a word processor
• Color depth is measured in bits and indicates the
  number of colors a scanner can detect

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Resolution

• Resolution determines the amount of detail a
  scanner can detect
• Ranges from 600 dpi to 2400 dpi
• You usually dont need to scan at a higher
  resolution than a printer can produce or a
  monitor can display
• Most monitors are 72 dpi
• Printers vary

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Output Devices
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Printers

• Speed of a printer is measured in pages per
  minute (PPM). A higher speed represents faster
  output
• Resolution determines the quality of images
• A higher resolution results in sharper images
• Printer resolution is measured in dots per inch
  (dpi)
• 600 dpi is acceptable 1200 is better for images
• Resolution expressed with two numbers represents
  dots per inch across and down

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Types of Printers

• Ink-jet has a print head that sprays ink through
  tiny nozzles onto a page
• 2 to 10 pages (ppm)
• 360 to 2400 dots per inch
• Color printers spray cyan, magenta, yellow and
  black to create different colors
• Laser-printer
• Works like a photo copier
• Speed of 4 to 16 pages
• Have a CPU
• 600 to 2400
• Memory 2mb to 8 Mb

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Print Buffer and Spoolers

• Printer buffer section of memory printer stores
  information waiting to print
• Printer spooler program on your computer that
  stores information waiting to print
• Stores more information than the buffer
• One spooler for each connected printer

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Monitors

• Video cards translate instructions from the
  computer into a form Most computes the monitor
  can understand
• require at least 2 mb of video card memory

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Monitor Metrics

• The smaller the dot pitch, the crisper the image
• 0.28mm is acceptable
• Refresh rate is measured in hertz (Hz)
• Times per second computer redraws the image
• 72 Hz or more is acceptable

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Communications

• Modems let a computer exchange information
  through telephone lines
• Speed of a modem determines how fast it sends and
  receives messages
• 56,000 bps (56 Kbps)
• V.90 standard receive 56K and send 33.6K
• Speed at which information flows depend on the
  quality of the phone line

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High-speed Connections

• ISDN Integrated Services Digital Network
• Digital phone line
• 56 Kbps to 128 Kbps
• Cable Modem
• Same cable as TV
• 4000 Kbps
• DSL Digital subscriber line
• High speed digital phone line
• 1000 6000 Kbps

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Operating Systems
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Operating Systems

• Software that controls the overall activity of
  the computer
• Ensure that all of the parts of the computer work
  together smoothly
• Functions
• Control hardware
• Run software
• Manage information
• Programs that run on one operating system
  platform do not generally run on others

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Software Systems Software

• Operating systems
• Controls the hardware components (disks, CPU,
  printers, etc.)
• Windows XP, Windows NT/2000, Windows 9-X, MS-DOS,
  OS/2, MacOS, Unix, Linux, BeOS

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Types of Operating Systems

• MS-DOS
• Command driven
• Windows
• Windows 3.1
• Windows 9X (95, 98)
• Windows ME
• Windows XP
• Windows NT
• Windows 2000
• UNIX
• MAC OS

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Unix

• Can run single computer or entire network
• Developed on mainframes in late 60s
• True multi-tasking OS
• Most widely used operating system on Internet

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LINUX

• Unix-based system offered as freeware on the
  Internet

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Software
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Software

• System software runs the machine
• Application software helps you accomplish
  specific tasks
• Manufacturers also may create minor software
  updates called patches, to make corrections or
  improvements to software

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Utility Programs

• Utility A program that performs a specific task
  on your computer
• Norton utilities recover files
• Virusscan anti-virus software
• Acrobat Reader View PDF (Portable Document
  Format) files
• Winfax pro
• ViaVoice Speech recognition
• WinZip Compress and decompress files

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Application Software

• Word processor
• Spreadsheets
• Presentation Software
• Database Software
• Internet Software

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Software Application Software

• Office products
• Word processors
• Spread sheets
• Presentation software
• Email
• Business applications
• General ledger
• Financials
• Accounts payable
• Accounts receivable
• HRMS
• Fixed assets/inventory

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Database Programs

• Helps you manage large collections of related
  information
• Uses
• Store information
• Find information
• Analyze and print information

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Databases

• Organized in
• Tables
• Collection of information about a specific topic
• Field
• Category of information
• Record
• Single instance of information

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Programming Software

• Text Editor
• Used by the programmer while coding the program
  in a programming language
• Like a word processor - creates a text file
  containing the program's instructions or "source
  code"
• Examples are nled and vi editors in Unix
  systems
• Other editors are NotePad and WordPad which are
  text-based

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Programming Software

• Interpreters
• Translates source code into machine code line by
  line
• Compiler
• Translates source code into an object file, than
  uses linker to create an executable file
• A source module (source code) becomes an "object"
  module (compiled module)
• Then it is linked with system modules to become a
  "load" module (linked module)
• It is usually more efficient to use a compiler