Chapter 1b Introduction

7/30/2019 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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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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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


Data

Storage

Facility

Data

Processing

Facility


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Operation (3)

Processing from/to storage

e.g. updating bank statement

Data

Movement


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


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

Chapter 1b Introduction

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