Download - Chapter 1b Introduction
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Chapter 1b
Introduction
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Objectives
By the end of this lecture, the student shouldbe able to: Differentiate between computer architecture and
computer organisation
Differentiate the structure and function of thecomputer
Give a brief description of the main functions of thecomputer
Describe the computer as an hierarchical system Give a brief description of the function of the main
components of the computer
Have an understanding the reasons for the course
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Questions
What is a computer?
In day-to-day life, what are some of the usesof computers?
Name three main components of a computer What would you consider to be the most
important component of the computer?
What is the difference between a degree in
Information Technology (IT) and one inComputer Science?
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Architecture & Organization 1
Architecture is those attributes visible to theprogrammer; those that have a direct impacton the logical execution of a program Instruction set, number of bits used for data
representation, I/O mechanisms, memoryaddressing techniques.
e.g. Is there a multiply instruction?
Organization is how features are implemented;
the operation units and their interconnectionsthat realize the architectural specifications Control signals, interfaces, memory technology.
e.g. Is there a hardware multiply unit or is it done by
repeated addition?
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Architecture & Organization 2
It is important for computer scientists to knowthe difference between computer architectureand computer organisation .
Most computer manufacturers offer a family of
computer models, all with the samearchitecture but different organisation; thisbrings the differences in pricing.
Organisation or Architecture; which one do we
study? A computer organisation must be designed to
implement a particular architecture; studyingorganisation implies studying architecture as well
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Architecture & Organization 3
All Intel x86 family share the same basic
architecture
The IBM System/370 family share the
same basic architecture
This gives code compatibility
At least backwards
Organisation differs between different
versions
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Structure & Function
A computer is complex system that is made upof sub-systems which are organised in anhierarchical manner
Structure is the way in which componentsrelate to each other
Function is the operation of individualcomponents as part of the structure
The hierarchy of a system can either be donetop-down orbottom-up. Top-down is clearerand most effective.
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Functions of the Computer
All computer functions are:
Data processing
Data storage both short-term and long -
term
Data movement between itself and the
outside world. This is done via peripheral
devices (directly connected to the computer)or remote devices (data communication)
Control
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Functional view
Functional view of a computer
Data
Movement
ApparatusControlMechanism
Data
Storage
Facility
Data
Processing
Facility
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Operations (2)
Storage
e.g. Internet download to disk
Data
Movement
ApparatusControlMechanism
Data
Storage
Facility
Data
Processing
Facility
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Operation (3)
Processing from/to storage
e.g. updating bank statement
Data
Movement
ApparatusControlMechanism
Data
Storage
Facility
Data
Processing
Facility
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Operation (4)
Processing from storage to I/O
e.g. printing a bank statement
Data
Movement
ApparatusControlMechanism
Data
Storage
Facility
Data
Processing
Facility
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Structure - Top Level
Computer
MainMemory
Input
Output
Systems
Interconnection
Communication
lines
CentralProcessing
Unit
Computer
There may be one or more of each of the
components
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Structure - The CPU
Computer ArithmeticandLogin Unit
Control
Unit
Internal CPU
Interconnection
Registers
CPU
I/O
Memory
System
Bus
CPU
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ALU Function
The arithmetic and logic unit (ALU)
performs arithmetic and logical operations
on data as directed by the control unit.
Data to be executed by the ALU istemporarily held in special purpose
memories located inside the processor
called registers.
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Structure - The Control Unit
CPU
Control
Memory
Control Unit
Registers and
Decoders
Sequencing
Login
Control
Unit
ALU
Registers
Internal
Bus
Control Unit
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CU Function
The control unit is responsible for
controlling all the activities of the
computer.
It controls communication between the
processor, main memory and
input/output devices via special
pathways known as system buses
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Main Memory
The main memory or primary storage
store data and instructions that are directly
accessible to the processor. The two main
types of primary storage are Randomaccess memory(RAM) and read on ly
memory (ROM).
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RAM
RAM mostly referred to as working storage is
a volatile, temporary storage that holds input
entered into the computer for processing andoutput after processing
ROM
ROM contains nonvolatile, relativelypermanent data and instructions that cannot
be easily changed.
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Why this course?
To not only understand how computers workbut also why they work the way they do; not to
regard a computer as a black box
To acquire some understanding and appreciation of
computer components characteristics, performanceand interactions
To be able to structure programs that run on the
computers
To be able to make correct choices of computersfor various tasks