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Computer system

Computer System

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Book I: computer system fundamentals.

Chapter 1: INTRODUCTION TO COMPUTER.

Question 1. What is a computer?

A computer may be defined as a machine which accepts data from an input device, processes it

by performing arithmetical and logic operations in accordance with a program of instructions and

returns the results through an output unit.

A computer is basically an electronic machine operating on current.

Question 2. Components of a Computer system?

A computer system comprises of the following components:

1. Central Processing Unit (CPU).

- CPU is the heart of the whole sys

- CPU consists of the :

• control unit (CU)

• arithmetic logic unit (ALU)

• accumulator (ACC)

• program counter (PC)

• instruction register (IR)

• memory address register (MAR)

• memory data register (MDR)

• status register (SR)

• general purpose register

- The function of each components of CPU:

• Control unit:

 control and co_ordinate all hardware functions of the CS.

 examine and decode all program instructions to the computer and

initiate their execution by sending the appropriate signals.

• ALU:

 performs all arithmetic <addition, subtraction, multiplication,

division & exponentiation> and logic comparision two values

functions required by computer.

• ACC:

 holds the first operand of the temporary result of the ALU.

• PC:

 contains the add of the next instruction to be excuted.

• IR:

 contains the current instruction to be executed.

Main memory

• MAR:

 holds the address location to or from which data is to be transferred

• MDR:

 contains the data to be written to or read out of the addressed

location.

• SR:

 keeps track of the status of the accumalator.

• General Purpose Register:

 for general purpose procedures.

Please refer to diagram for an illustratin of the basic components of the CPU.

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CPU

Control unit

Arithmetic Logic Unit

Accumulator

Program Couter to main

Instruction Register memory

Memory Address Register

Memory Data Register

Status Register

General Purpose Register

Basic components of a CPU.

Control Unit

Input Unit ALU Output Unit

Main Memory

Backing Storage

Control signals

Data flow

Components of a CS.

2. Input units

- Used to enter data( raw unprocessed facts) and instructions to the computer.

3. Output units

- Used for delevering the processed result from the computer in useful form.

4. Backing storage units

- Backing storage units need for high capacity data storage devices that can store

data in a more permanent form for later retrieral, updating and referencing.

- Backing storage is also called secondary storage external storage and auxiliary

storage.

Chapter 2: MICOPROCESSOR.

Question 1. Cache Memory?

- Cache memory is a small amount of very fast store with faster access time than

the main memory.

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