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Module 3Module 3
Introduction To Computer System :
Structure & Processes
Introduction To Computer System :
Structure & Processes
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Module ObjectivesModule Objectives
At the end of the module, students should be able to:
understand the concept and functions of a computer system
identify the component of a computer
identify the components of the central processing unit and
explain how they work together and interact with memory
describe how program instructions are executed by the
computer
explain how data is represented in the computer
understand the concept of bit and byte
identify the types of ports and connectors
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What is A Computer System ?What is A Computer System ?
A functional unit, consisting of one or more
computers and associated software, that uses
common storage for the execution of the
program. Consists of three components
People
Computer programmer
Users/End-user
Software
Hardware
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Functions Of A Computer SystemFunctions Of A Computer System
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Components Of A ComputerComponents Of A Computer
Systems
Interconnection
i.e. bus
CPU
Main
Memory
Input /Output
Communication Lines
PeripheralsComputer
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Complex set of
electronic
circuitry
Executes storedprogram
instructions
Two parts
Control unit
Arithmetic/logic
unit (ALU)
Central Processing UnitCentral Processing Unit
Sends
data to
the CPU
Registers
Control
Unit
ALU
Unit
Processing
InputOutput
Secondary storage
Stores data and programs
Makes
processed
info
available
Central Processing Unit
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Control UnitControl Unit
Directs the computer system to execute
stored program instructions
Must communicate with memory and ALU
Sends data and instructions from
secondary storage to memory as needed
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Arithmetic Logic UnitArithmetic Logic Unit
Executes all arithmetic and logical operations
Arithmetic operations
Addition, subtraction, multiplication, division
Logical operations
Compare numbers, letters, or special characters
Tests for one of three conditions
Equal-to condition
Less-than condition
Greater-than condition
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Intel AdvancedMicro Devices
(AMD)
Cyrix Motorola (Apple)
Pentium IVPentium MMX
Pentium III
Popular CPUsPopular CPUs
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shared communication link
set of wires used to connect multiple subsystems
A Bus is also a fundamental tool for composing
large, complex systems The input/output bus provides a pathway so that themicroprocessor can communicate with input/outputdevices
Systems Interconnection (Bus)Systems Interconnection (Bus)
Control
Data
path
Memory
Processor
Input
Output
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Input / Output BusInput / Output Bus
An input/output bus contains expansionslots which hold expansion cards ISA (Industry Standard Architecture) slotphased out
PCI (Peripheral Component Interconnect) slots
AGP (Accelerated Graphics Port) slot usually forgraphics card
USB (Universal Serial Bus)
PCI Express (PCI-E) latest tech.
PCI slots
Expansion CardAGP slots PCI-E slots
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Data Storage and the CPUData Storage and the CPU
Two types of storage:
Primary storage (memory)
Stores data temporarily / volatile
CPU refers to it for both program
instructions and data Holds input to be processed or holds
results of processing
Secondary storage
Long-term storage / non-volatile
Stored on external medium, such as a disk
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The CPU and MemoryThe CPU and Memory
CPU cannot process data from disk or input device
It must first reside in memory
Control unit retrieves data from disk and moves it into memory
Items sent to ALU for processing
Control unit sends items to ALU, then sends back to memory after
processing
Data and instructions held in memory until sent to an
output or storage device or program is shut down
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Temporary Storage AreasTemporary Storage Areas
High-speed temporary
storage areas
located within the CPU
Work under direction of
control unit
Accept, hold, and transfer
instructions or data
Keep track of where thenext instruction to be
executed or needed data is
stored
Also known as primary
storage / main memory
Often expressed as random-
access memory (RAM)
Not part of the CPU
Holds data and
instructions for processing
Stores information only as
long as the program is in
operation
MemoryRegisters
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The Machine CycleThe Machine Cycle
The time required toretrieve, execute,and store an
operation Components
Instruction time
Execution time System clock
synchronizesoperations
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The Machine CycleThe Machine Cycle
Instruction Time = I-Time Fetch Gets thenext program instruction from the
computers memory
Decode Figures out what the program is telling thecomputer to do
Execution Time= E-Time Execute Performs the requested action
Write-back (Store) Writes (stores) the results to a
register or to memory
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OFFON
0 1
OR = 1 bit
1
0
0 0 001 1
0 0 0 01 1
OR
= 1 Byte
= 1 Byte
OFF
0
0
How Computers Represent DataHow Computers Represent Data
Bit (Binary digit) On or off state of electric current; considered the
basic unit of information; represented by 1s and 0s (binary numbers)
Byte Eight bits grouped together to represent a character (an
alphabetical letter, a number, or a punctuation symbol); 256 different
combinations
ON
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1000 bits = 1 kilobit (kb)
1,000,000bits = 1 megabit (mb)
1,000,000,000 bits = 1 gigabit (gb)
Kilobits per second (Kbps), Megabits persecond (Mbps), and Gigabits per second(Gbps) are terms that describe units of data
used in measuring data transfer rates Example: 56 Kbps modem
BitsBits
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BytesBytes
8 bits = 1 Byte
1024 Bytes = 1 Kilobyte (KB)
1,048,576 Bytes = 1 Megabyte (MB)
1,043,741,824 Bytes = 1 Gigabyte (GB)
1,099,511,627,776 Bytes = 1 Terabyte (TB)
Kilobyte, megabyte, gigabyte, and terabyte are terms
that describe large units of data used in measuring datastorage
Example: 20 GB hard drive
Each byte has 256 (28) possible values
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Kilobyte:1024 (210) bytes Memory capacity of older personal computers
Megabyte: roughly one million (220) bytes
Personal computer memory Portable storage devices (diskette, CD-ROM)
Gigabyte: roughly one billion (230) bytes Storage devices (hard drives)
Mainframe and network server memory
Terabyte: roughly one trillion (240) bytes Storage devices on very large systems
Storage SizesStorage Sizes
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Coding SchemesCoding Schemes
Provide a common way of representing a
character of data
Needed so computers can exchange data
Common Schemes
ASCII
EBCDIC
Unicode
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0 10 0 001 1
= 4
= 4
Representing Characters : Character CodesRepresenting Characters : Character Codes
Character codes translate numerical data intocharacters readable by humans
American Standard Code for Information Interchange
(ASCII) Eight bits equals one character; used by
minicomputers and personal computers
Extended Binary Coded Decimal Interchange Code
(EBCDIC) Eight bits equals one character; used by
mainframe computers
Unicode Sixteen bits equals one character; over 65,000
combinations; used for foreign language symbols
ASCII
0 001 11 1 1
EBCDIC
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Inside the System Unit / CasingInside the System Unit / Casing
Motherboard (mainboard) Largeprinted circuit board with thousandsof electrical circuits
Power supply Transforms
alternating current (AC) from walloutlets to direct current (DC)needed by the computer
Cooling fan Keeps the systemunit cool
Internal Speaker Used for beepswhen errors are encountered
Drive bays Housing for thecomputers hard drive, floppy drive,and CD-ROM / DVD-ROM drives
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Drive bays
On/off switch
Reset button
Indicator lights
FRONT
BACK
The front panel contains drive bays, various buttons, andindicatorlights
Connectors and ports are physical receptacles locatedon the back to connect peripheral devices to the computer
Outside the System UnitOutside the System Unit
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Types of Connectors / PortsTypes of Connectors / Ports
A 15 pin connector
used for monitors
For graphics-intensive
interaction
Data flows through eight wires allowing
the transfer of eight bits of data
simultaneously; faster than serial ports
Allows up to
127 devices
to be
connected at
a time.
keyboard
port -
Special
serial port
to connect
keyboard.
Mouse
portSpecial
serial port
to connect
mouse.
Also called jacks,
sound card connectors
accept stereo mini-
plugs. Microphone,
line-in, line-out, and
speaker connectors
are plugged into thecard.
Serial port Data
flows in a series of
pulses, one after
another one bit at
a time; slow data
transfer rate.
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Other Types of ConnectorsOther Types of Connectors
Small computer system interface (SCSI) port
A parallel interface that enables up to eight
devices to be connected to it
1394 (FireWire) port A high-speed
connection for up to 63 devices
Infrared Data Association (IrDa) port
Infrared signals are used to communicatebetween peripheral devices and the system
unit
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ReferencesReferences
Slides adapted from course materials of
Daley, B. Computers Are Your Future
2006, Complete Ed. Prentice Hall, 2006.
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