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Chapter 2 Computer System Architecture

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. Motorola Intel

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Chapter 2 Computer System Architecture

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  1. Chapter 2Computer SystemArchitecture

  2. Phases of Activity • Input • Processing • Output • Storage

  3. Computer system architecture • Hardware • Software software computer hardware

  4. Computer Hardware • CPU (Central Processing Unit) • Arithmetic/Logic Unit • Control Unit • eg. Motorola Intel APPLE IBM 6502 APPLE II 8088 PC/XT 68010 80286 PC/AT 68020 80386 68030 80486 68040 MAC 80586 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 ...

  5. Computer Hardware CPU Control Unit Arithmetic/ Logic Unit Output Device Main Memory Input Device

  6. 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 ...

  7. 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

  8. 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

  9. 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

  10. 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)

  11. 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

  12. 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

  13. Data representation • Numeric value representation: • hexidecimal digit : base 16 0000 : 0 1000 : 8 0001 : 1 1001 : 9 0010 : 2 1010 : A 0011 : 3 1011 : B 0100 : 4 1100 : C 0101 : 5 1101 : D 0110 : 6 1110 : E 0111 : 7 1111 : 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?

  14. 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.

  15. Numeric value : Integers • Two's complement notation: • easy to do arithmetic operations. • eg. 0111 : 7 1111 : -1 0110 : 6 1110 : -2 0101 : 5 1101 : -3 0100 : 4 1100 : -4 0011 : 3 1011 : -5 0010 : 2 1010 : -6 0001 : 1 1001 : -7 0000 : 0 1000 : -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)

  16. 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.

  17. 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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