Title: Computer Operation

Subject: Computer Studies

EDD 5161 F

Educational Communication & Technology

About the author …

Name of student:

Fok Yan Ming

Student ID:

98039900

Introduction

The target audience are form 4 students.

This slide show will be presented as a lecture.

Computer Operation

What can you find in a personal computer?

Input device Input device

Output device

How about this case?

What can you find

In my body?

Central Processing Unit (CPU)

Control Unit (CU) It coordinate machine activities.

Arithmetic and Logic Unit (ALU) It performs data manipulation.

Memory Unit (This name is seldom used)

It accesses the main memory cells.

There are some components in each unit.

Control Unit Program Counter

Instruction Register

Instruction Decoder

Arithmetic and Logic Unit Accumulator

Status Register

Logic Circuit

Memory Unit Memory Data Register

Memory Address Register

Address Decoder

In Control Unit (CU)Program counter (PC)

To hold the address of the next instruction. Instruction register (IR)

To hold the instruction currently executed. Instruction decoder

To decode the instruction.

Let’s see how the control unit works!

Box 1

Box 2

Box 3

The Treasure Boxes

Clean theboard

See theteacher

CollectThe forms

Now the teacher give you three treasure boxes. Each box contain a command from the teacher.

You cannot open the boxes or read the commands yourself. The monitor knows which box should be opened and the monitress reads the command inside the box.

Box 1

Box 2

Box 3

The Treasure Boxes

Clean theboard

See theteacher

CollectThe forms

Box 1

The monitor knows which box should be opened.

Box 1

Box 2

Box 3

The Treasure Boxes

Clean theboard

See theteacher

CollectThe forms

Box 1

The monitress reads the commands.

Box 2

At the same time, the monitorprepares to show you the nextbox should be opened.

Box 1

Box 2

Box 3

The Treasure Boxes

Clean theboard

See theteacher

CollectThe forms

But you don’t knowEnglish! Oh!

?

Box 1

Box 2

Box 3

The Treasure Boxes

Clean theboard

See theteacher

CollectThe forms叫你擦黑板呀！

哦，我明白啦！

Box 1

Box 2

Box 3

The Treasure Boxes

Clean theboard

See theteacher

CollectThe forms

The monitor plays the role ofProgram Counter.

The monitress plays the role ofInstruction register.

The translator plays the role ofInstruction decoder.

Interpretation

001

010

011

Main Memory

Inp A

Sto B

End

::::

001Program Counter

Inp AInstruction Register

Program Decoder

In Arithmetic & Logic Unit (ALU)

Accumulator (ACC) To hold the result or intermediate result of

the operation temporarily.Status register (SR)

To hold the status flag which show the status of the content in the accumulator.

Logic circuit To perform arithmetic and logic operation.

AccumulatorThe accumulator acts as the note pad. You can jot down the intermediate result (or final result) of your calculation.

For example, when evaluating

(7.9 + 1.7) (2.4 – 1.8)

You better jot the result

(7.9 + 1.7) and (2.4 – 1.8)

on the note pad, right?

Status Register

It describes the current status of the accumulator.

When 0 or 1 is assigned to the flags in status register, the status can be shown.

For example,

9Accumulator

Status Register

odd integer positive zero

-2

Interpretation

In this example, we only have four flags.

You may imagine that if we have many flags….

we can describe the content in the accumulator accurately

Memory Data register (MDR) To hold the data or instruction to be stored

in or fetched from main memory.Memory Address register (MAR)

To hold the address of the memory location to be accessed.

Address Decoder To location the memory cell whose address

is stored in MAR.

In Memory Unit

In the previous example about control unit, the instruction seems to be accessed directly.Actually, we must access the main memory via the MAR and MDR.

Now lets see an demonstration.

001

010

011

Main Memory

Inp A

Sto B

End

:::

001

Program Counter

Inp A

Instruction Register

MAR

MDR

Address Decoder

001

Inp AInp A

Instruction decoder

IR PC

CU

Logic circuit

SR

ACC

ALU

Address decoder

MAR

Memory Unit

MDR

The Central Processing Unit

Summary

This is the end.

Click the button to exit.