Chapter 2 computer system architecture
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Chapter 2 Computer System Architecture. Phases of Activity. Input Processing Output Storage. Computer system architecture. Hardware Software. software. computer hardware. Computer Hardware. CPU (Central Processing Unit) Arithmetic/Logic Unit Control Unit eg.MotorolaIntel

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Chapter 2 Computer System Architecture

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Chapter 2 computer system architecture

Chapter 2Computer SystemArchitecture


Phases of activity

Phases of Activity

  • Input

  • Processing

  • Output

  • Storage


Computer system architecture

Computer system architecture

  • Hardware

  • Software

software

computer

hardware


Computer hardware

Computer Hardware

  • CPU (Central Processing Unit)

    • Arithmetic/Logic Unit

    • Control Unit

    • eg.MotorolaIntel

      APPLEIBM

      6502 APPLE II

      8088 PC/XT

      6801080286 PC/AT

      6802080386

      6803080486

      68040 MAC80586

      Pentium/II/III

  • Input device

    • keyboard, mouse, card reader, scanner ...

  • Output device

    • monitor, printer, plotter ...

  • Memory

    • main memory : (human's brain)

      • fast, expensive

      • memory chip

    • secondary memory: (auxiliary memory)

      • slow, cheap

      • diskette, tape, CD-ROM ...


Computer hardware1

Computer Hardware

CPU

Control

Unit

Arithmetic/

Logic

Unit

Output

Device

Main

Memory

Input

Device


Computer software

Computer Software

  • System software

    • Operating system (OS)

      • DOS (Disk Operating System)

      • WINDOWS 95/98

      • WINDOWS NT 4.0/WINDOWS 2000

      • UNIX/Linux

  • Application software:

    • Accounting, Payroll, Inventory, etc.

  • Utility:

    • Pctools, Norton Utility ...


Input hardware

Input hardware

  • Keyboard

    • standard typewriter keys are used to type in the text and other data

    • function keys, F1, F2 ...

    • special-purpose keys, such as Alt, Ctrl, Ins, Del ...

    • cursor movement keys

    • numeric keys

  • Card reader

  • Scanner :

    • OCR (Optical Character Recognition)

  • Bar code reader

  • Magnetic-Ink Character Recognition

  • Voice input device

  • Mouse

  • Light pen

  • Trackball

  • Touch screen

  • Digitizers


Chapter 2 computer system architecture

Output hardware

  • Can divide into two categories : Hard copy and Soft copy.

  • Soft copy :

  • Monitor

    • Monochrome

    • RGB

    • Plat panel

  • Sound

  • Hard copy :

  • Printer

    • Impact : Dot Matrix, Line printer, Daisy wheel, Chain printer

    • Non-impact : Laser printer, Ink-jet printer, Thermal printer.

  • Plotter

  • Punches (Tapes, Cards)

  • COM (Microfiche, Microfilm)

  • Computer-Usable Storage

    • Diskettes, H.D., Optical disk, Tape


Chapter 2 computer system architecture

Processing hardware

  • Central Processing Unit

    • Arithmetic Unit

    • Logic Unit

    • Control Unit

    • Register:

      • A special memory cell within CPU.

      • Used as temporary holding places for data being manipulated. e.g., Accumulator, Program counter


Storage hardware

Storage hardware

  • Primary storage:

    • the computer's main memory, where data and instructions are held for immediate access and use by the computer's CPU during processing.

    • volatile

    • memory cell : managable memory unit

    • address

      • To identify each individual cells in a machine's main memory, each cell is assigned an unique name, called its address.

  • Secondary storage:

    • retains data and instructions in a more permanent form

    • tape:

      • inter-record gap

    • disk:

      • sector

      • track

      • cylinder

  • Data retrieval method:

    • Sequential access

    • Direct access

    • Indexed sequential access method (ISAM)


Data representation

Data representation

  • Binary digit : BIT

    • 0 or 1, on or off, yes or no ...

  • Byte : 8 bits.

  • Binary code :

    • a scheme for encoding data using a series of binary digits (bits).

  • Character symbol representation:

    • ASCII:

      • American Standard Code for Information interchange

      • use 8 bits to represent one character but only 7 bits are meaningful.

      • "A" = 01000001

      • Page 128

    • BCD :

      • Binary Coded Decimal


Data representation1

Data representation

  • Numeric value representation:

    • BCD

      • 13 : 0001 0011

    • binary digit :

      13

      = 8 + 4 + 1

      = 1*23 + 1*22 + 0*21 + 1*20

      = (1101)2

    • binary system : base 2

      • MSB : most significant bit

      • LSB : least significant bit

    • disadvantage:

      • hard to read

    • eg.

      1100111011010010

      1100110010010011


Data representation2

Data representation

  • Numeric value representation:

    • hexidecimal digit : base 16

      0000 : 01000 : 8

      0001 : 11001 : 9

      0010 : 21010 : A

      0011 : 31011 : B

      0100 : 41100 : C

      0101 : 51101 : D

      0110 : 6 1110 : E

      0111 : 71111 : F

      eg .

      1100 1110 1101 0010 : C E D 2

      1100 1100 1001 0011 : C C 9 3

  • binary addition:

    13 1101

    + 7 + 0111

    ----------------

    20 10100

  • binary subtraction:

    • 13 - 7 = 13 + (-7)

  • How do we represent negative value?


Numeric value integers

Numeric value : Integers

  • Sign magnitude notation:

    • sign bit : MSB

      • 0 : positive , 1 : negative

    • eg.

      • 00001001 => 9

      • 10001001 => -9

  • Excess notation:

    • bit pattern length

    • eg.

      111 : 3

      110 : 2

      101 : 1

      100 : 0

      011 : -1

      010 : -2

      001 : -3

      000 : -4

    • Excess 4 notation :

      • each of the traditional binary values exceeds the value being represented in the code by 4.

    • disadvantage:

      • hard to do arithmetic operations.


Numeric value integers1

Numeric value : Integers

  • Two's complement notation:

    • easy to do arithmetic operations.

    • eg.

      0111 : 71111 : -1

      0110 : 61110 : -2

      0101 : 51101 : -3

      0100 : 41100 : -4

      0011 : 31011 : -5

      0010 : 21010 : -6

      0001 : 1 1001 : -7

      0000 : 01000 : -8

    • MSB :

      • 0 : positive

      • 1 : negative

    • complement :

      • 0101 : 5

      • 1010 : complement

      • 1011 : +1 = -5

    • addition in 2's complement notation:

      • 7 - 4 = 7 + (-4)

      • (0111) + (1100)

      • 10011

      • 0011 (truncate)


Numeric value integers2

Numeric value : Integers

  • Two's complement notation:

    • 4 - 7 = 4 + (-7)

    • (0100) + (1001)

    • 1101

    • (-3)

  • Overflow:

    • In any of the numeric systems, there is a limit to the size of the values that can be represented.

    • eg.

      • when use 2's complement notation with 4 bits

      • 9 has no pattern associated with it

      • 5 + 4 <> 9, 5 + 4 = -7

    • overflow problem

  • how to detect the overflow problem when using 2's complement notation to do arithmetic operation ?

  • Double precision :

    • the length of the patterns used is doubled from that which the machine normally uses.


  • Numeric value fractions

    Numeric value : Fractions

    • It must represent the position of radix point.

    • Floating point notation:

      • sign bit

      • exponent

      • mantissa

    • eg.

      • sign bit : 1

      • exponent : 3

      • mantissa : 4

      • 01101011

      • 10.11

    • Round-off error

      • eg.

        • 2 (5/8)

        • 10.101

        • 10.10


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