the central processing

8/6/2019 The Central Processing

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OBJECTIVES :

Identify the components of the central processing unit andhow they work together and interact with memory

Describe how program instructions are executed by thecomputer

Explain how data is represented in the computer

Describe how the computer finds instructions and data

Describe the components of a microcomputer system unitsmotherboard


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THE CPUComplex set of electronic

circuitry

Complex set of electroniccircuitry

Set of electronic circuitrythat executes stored

program instructions

Set of electronic circuitrythat executes stored

program instructions

Control center

Control center

Two parts Control Unit (CU)Arithmetic LogicUnit (ALU)

Two parts Control Unit (CU)Arithmetic LogicUnit (ALU)


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y Long-term storage of memory

y Data not lost when computer shut down

y Examples include hard drive, diskette, DVD-ROM


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Two types of storage:

Primary storage

(memory) Stores data

temporarily

CPU refers to itfor both programinstructions anddata

Secondary storage

Long-termstorage

Stored on externalmedium, such as adisk


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y 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

y Items sent to ALU for processing Control unit sends items to ALU, then sends back to

memory after processing

y Data and instructions held in memory until sent to anoutput or storage device or program is shut down


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Central Processing Unit is the core component

of a computer. It executes users instructionsand processes calculations.

Central Processing Unit is the core component

of a computer. It executes users instructionsand processes calculations.

Without the CPU, the devices cannot worktogether and so the computer cannot

function

Without the CPU, the devices cannot worktogether and so the computer cannot

function

Like the chief commander of an army, theCPU controls and co-ordinates various

devices in the computer system.

Like the chief commander of an army, theCPU controls and co-ordinates various

devices in the computer system.


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THERE ARE TWO TYPES OF PROCESSORS

TYPE I - Sockettype

TYPE II - SLOTTYPE

Pin arrangement in theSocket type processor is known as

PinGrid Array (PGA).

Slot type processor is alsoCartridge(SECC)


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CPU is often etched on a chip and is usually

called a microprocessor.

Intel Pentium III

Cyrix II Intel Pentium 4

AMD Athlon XP


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y Central processing unit etched on silicon chip

y Contain tens of millions of tiny transistors

y Key components: Central processing unit

Registers

System clock


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y Computers use the binary system to store and processinformation.

In the binary system, there are only numbers 0 and 1,which are called binary digits.

y Music is stored as a sequence of 1s and 0s in the

computer


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y All sorts of information, such as text,sound and graphics, can be stored asa sequence of binary digits (bit pattern)


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Bit Byte Word Short for binary digit

Two possible values:

0 and 1

Can never be empty

Basic unit for storing data0 means off, 1 means on

A group of 8 bits

Each byte has 256 (28)

possible values

For text, stores onecharacter

Can be letter, digit, orspecial character

Memory and storagedevices measured innumber of bytes

The number of bits theCPU processes as a unit

T

ypically a whole numberof bytes

The larger the word, themore powerful thecomputer

Personal computerstypically 32 or 64 bits inlength


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FETCHINGy The control unit gets the next

program instruction from the mainmemory.

DECODINGy The control unit decodes what the instruction Means

EXECUTING

y The ALU executes arithmetic andlogical instructions. It means that theALU controls and performs the actualoperation on the data.

Program Executions


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y The control unit executes theinstructions, sends control signals toand receive control signals from

peripheral devices.

y In other words, it controls the wholecomputer, and directs the entire system to

carry out instructions.


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Addition, subtraction,

multiplication, divisionArithmeticandLogic Unit

Arithmeticunit

Logic unit

Compare numbers,letters, or special

characters


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y When the control unit and thearithmetic and logic unit operate, theystore the information and instruction

temporarily in registers.


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Before a computer executes instructions, they

are first placed in the main memory.

The diagram shows how the CPUexecutes an instruction :

This is called

MACHINE CYCLE


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y Houses the electronic component of the computersystem

Motherboard


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y Flat circuit board thatholds the computercircuitry Central processing unit

(microprocessor) is mostimportant component

the central processing

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