1' ORGANIZATIONAL FOUNDATIONS OF INFORMATION SYSTEMS

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Computers and Information Processing (Chapter
6) http//teaching.ust.hk/ismt101/
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Objectives of This Lecture

• How Computers Represent Data
• Computer System Configuration
• Categories of Computers

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How computers represent data

• Bit (binary digit)
• smallest unit of data with 2 possible states (0
  or 1)
• Byte
• a string of 8 bits to represent a character

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Number Systems
Humans represent numbers in Base10
Digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Numeric Expression
Decimal Value
1 x 103 1,000 9 x 102 900 9 x 101
90 9 x 100 9
1999
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Computers use Base2 (0 and 1)
1 0 1 1 1 0 1
Base2 expression
Decimal Value
64 0 16 8 4 0 1 93
Base2 1011101

Base10 1 x 26 0 x 25 1 x 24 1 x
23 1 x 22 0 x 21 1 x 20
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Class Exercise
1
12
64
2
28
70
60
81
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Coding Schemes

• Coding schemes (to represent all characters)
• ASCII
• EBCDIC
• BIG-5 (chinese characters)
• UNICODE (uses 16 bits)
• for all characters in all languages
• http//www.unicode.org/

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Computer System Configuration

• Central Processing Unit (CPU)
• Primary storage (or main memory)
• Secondary storage
• Input devices
• Output devices
• Communication devices

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Computer Hardware - Class Exercise
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Hardware System

• Input
• i) Keyboard
• ii) Mouse
• iii) Microphone
• Output
• iv) Printer
• v) Monitor
• vi) Speaker
• Processing
• Tower Case Box

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Hardware Components of Computer System
CPU
Secondary Storage
Input Devices
Buses
Communications Devices
Output Devices
Primary Storage
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CPU
Control Unit
Flash Memory
PROM
ROM
Decoder
Program Register
Buses
Secondary Storage
Cache
Instruction Register
RAM
General-purpose Register
Arithmetic and Logic Unit
Accumulator
General-purpose Register
Communication Devices
Output Devices
Input Devices
General-purpose Register
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Computer time
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Blinking an eye
1 blink takes 1/10 of a second 1/10 s 100
million ns a computer can perform operations in
as little as 10 ns no. of operation 100
million/10 10 million thus, one blink of an
eye 10 million operations
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Memory and storage sizes
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Central Processing Unit (CPU)

• Manipulates data and controls other parts of the
  computer system
• Consists of 2 parts
• Control Unit
• Arithmetic-Logic Unit (ALU)

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Cache memory chip
CPU chip
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Machine Cycle

• A machine cycle is a series of operations that
  are necessary to process a single program
  instruction involving
• Control Unit
• ALU
• Primary Storage

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Control Unit

• Reads and interprets program instructions, one at
  a time
• Direct internal processor components
• Control flow of programs and data in and out of
  RAM

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Steps in a machine cycle

• For every instruction, the control unit repeats a
  set of four basic operations
• fetch an instruction
• process of obtaining a program instruction or
  data item from memory
• decoding the instruction
• process of translating the instruction into
  commands the computer understand
• executing the instruction
• process of carry out the commands
• if necessary, storing the result
• process of writing the result to memory

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Diagram of a machine cycle
1. Fetch Instruction RAM to the Control Unit
2. Decode Instruction Control Unit
Instruction Time
4. Place Results in Memory ALU to RAM
Execution Time
3. Execute Instruction ALU
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Machine Time

• The time it takes to fetch and decode is called
  instruction time or I-time
• The time it takes to execute is called execution
  time or E-time
• Together they add up to the total time required
  for a machine cycle

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Diagram of machine time
CPU
Fetch Instruction
Control Unit
I-Time 1, 2
Decode Instruction
RAM
Bus
ALU
E-Time 3, 4
Execute Instruction
Place results in memory
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ALU

• Performs the execution part of a machine cycle
• artithmetic operations (,-,,/)
• comparsion operations (lt, gt, )
• logical operations (AND, OR)

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MIPS

• Some people measure a computer speed according to
  the number of instructions it can process in one
  second, or MIPS (Million of Instructions Per
  Second).
• Current PC can process more than 300 MIPS
• However, different instructions require different
  amounts of processing time, no real standard for
  measuring computer speed.

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Characteristics of Microprocessor

• 4 factors affecting the speed of the
  microprocessor
• word length (no. of bits processed in 1 machine
  cycle)
• clock cycle speed (MHz, million of cycles per
  second)
• 8088 (XT)-4.47 MHz
• Pentium II 450MHz, PowerPC 400 MHz,
• Pentium III 650MHz,
• 1000MHz (?)
• data bus width (8, 16, 32, 64 bits)
• CISC and RISC architecture

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CISC vs. RISC Architecture

• CISC (Complex Instruction Set Computing)
• usually only 20 of instruction set is used for
  80 of the computers tasks
• RISC (Reduced Instruction Set Computing)
• can execute more instructions in a single machine
  cycle
• PowerPC (Motorola, IBM, Apple)
• Sparc (by SUN), Alpha (by DEC)

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Functions of Primary Storage

• stores all or part of the program that is being
  executed
• stores the operating system (OS) programs that
  manage the operation of the computer
• stores data that are being used by the program

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Main Type of Primary Storage

• random access memory (RAM)
• volatile storage
• non-permanent, content are lost when power is off
• DRAM (Dynamic RAM)
• more commonly used (e.g. EDO DRAM, SDRAM)
• SRAM (Static RAM)
• faster, more expensive (use as cache memory)
• cache memory helps speed hte processes of the
  computer by storing frequently used instructions
  and data
• memory chips installed on SIMMs or DIMMs
• Single In-line Memory Modules (SIMMs)
• Dual In-Line Memory Modules (DIMMs)

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DIMM of RAM
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Other Types of Memory

• ROM
• read-only memory, data stored in ROM cannot be
  modified
• non-volatile
• contains instructions to start the computer
• PROM (programmable ROM)
• programmed only once
• used by manufactures as control devices in their
  products
• EPROM (erasable programmable ROM)
• used when the program may have to changed on a
  routine basis

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Secondary Storage

• Storage of data that is
• Relatively long-term
• nonvolatile storage
• outside the CPU and primary storage
• uses magnetic or optical technology
• involves mechanical parts

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Types of Secondary Storage

• Magnetic Tape
• sequential, slow, inexpensive
• Magnetic Disk
• DASD (Direct Access Storage Device), fast, more
  expensive
• Hard Disk, RAID
• Floppy Disk
• Optical Disk
• CD-ROM (660 MB), DVD (5 GB)
• WORM (Write Once/Read Many)
• rewritable magneto-optical disk

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Types of Input (identifique)
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Types of Input

• i) Data
• ii) User response
• iii) Programs
• iv) Commands

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Input Devices

• Keyboard, computer mouse, touch screen
• Source data automation
• magnetic ink character recognition e.g. checks
• optical character recognition (OCR) e.g. bar code
• pen-based input
• digital scanner
• voice input devices
• sensors

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Input Processing

• Batch processing
• transactions are accumulated and stored until a
  specified time when it is convenient or necessary
  to process them as a group
• e.g. payroll system, regular reporting
• Online processing
• transactions are entered directly into the
  computer system and processed immediately
• e.g. airline reservation, hotel reservation

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Batch Processing
Grouped transactions
Keyboard input
Reports
Validate and update
Sorted transaction file
Master file
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Online Processing
Keyboard input
Reports
Validate and update
Immediate input
Immediate processing
Master file
Immediate file update
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Output Devices

• Cathode ray tube (CRT) or video display terminal
  (VDT)
• printer
• plotter
• microfilm
• microfiche
• voice output device

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Categories of Computer

• Mainframe
• largest computer
• Minicomputer
• midrange computer
• Personal computer (PC) or microcomputer
• single user computer
• Workstation
• powerful graphics and computational capabilities
• Supercomputer
• for extremely fast and complex computations
• Server computer
• any of the above computers can be used to support
  sharing of files, software, printers, etc. on a
  network
• Network computer (NC)
• smaller, simpler, cheaper (ltUS1000), no
  secondary storage
• download software/data over the internet or LAN

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Sequential Processing
Program
Task 1
CPU
Result
Program
Task 2
CPU
Result
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Parallel Processing
Program
CPU Task 1
CPU Task 2
CPU Task 3
CPU Task 4
CPU Task 5
Result
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Where to find more information

• Magazines
• PC Computing, PC Magazine, PC World, Macworld
• http//www.zdnet.com/pccomp/filters/alist/
• Internet
• http//www.compaq.com
• http//www.apple.com
• http//www.intel.com
• CCST in HKUST
• http//www.ust.hk/ccst/desktop/

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