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Understanding Computer Components: CPU, Memory, Machine Cycle, and Buses, Slides of Computer Science

Punjabi UniversityComputer Science

An overview of various computer components, including the central processing unit (CPU), memory (RAM, ROM), disk drives, power supply, computer fan, and system clock. It explains the machine cycle, which is the process by which the CPU obtains instructions from memory, decodes and executes them, and stores results if necessary. The document also covers the concept of buses, which are electrical paths used to transfer data between components. Students will gain a better understanding of computer architecture and organization.

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Uploaded on 12/24/2021

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This book is compiled for all
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includes first 10 chapters (from
page 1 to 205) are related to
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practical.
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Download Understanding Computer Components: CPU, Memory, Machine Cycle, and Buses and more Slides Computer Science in PDF only on Docsity!

This book is compiled for all

BS/ADP disciplines. This book

includes first 10 chapters (from

page 1 to 205) are related to

computer concepts and other

chapters are related to the

Windows 7, MS office 2010

(Word, Excel, PowerPoint,

Access), and InPage 2000 with

practical.

Chapter 2

Components of the System

Unit

INTRODUCTION TO COMPUTER

System Unit

Chapter 2 - Components of the System Unit

System Unit

  • System unit is the main body of the computer
  • It is a case that contains different electronic components of the computer
  • These components include a central processing unit, memory (i.e. RAM, ROM), disk drives, power supply, computer fan, and other electronic components
  • All these components are connected to motherboard inside the system unit
  • All computers and mobile devices have a system unit
  • Input/output devices and some storage devices such as USB flash drive are connected with system unit
  • Different types of computers have system units of different shapes and sizes
  • In laptop computers, keyboard with a pointing device is built on the top of the system unit
  • Display screen is attached to system unit with hinges
  • Similarly, in mobile devices and many other mobile computers, display screen and keyboard are often built on system unit

Motherboard

  • Motherboard is the main circuit board of the system unit
  • It is also known as the system board or main board
  • It is the most important circuit board inside the system unit
  • Many electronic components are connected to motherboard and some

components are built into it

  • Processor chip and memory chips are plugged (installed) into motherboard
  • Motherboard contains sockets or slots on which electronic components are

installed

Central Processing Unit (CPU)

  • Simply called a CPU
  • It is the most important component of the computer
  • Also known as a processor
  • CPU is considered as the brain of the computer
  • It performs different operations on data according to given instructions
  • It also manages other operations of the computer
  • CPU used in a personal computer is known as a microprocessor
  • It consists of a single chip
  • It is located on motherboard inside the system unit
  • Today most of the processor chip manufacturers providing multi-core processors
  • A multi-core processor is a single chip that contains two or more processors
  • Each processor is called processor core or simply core
  • Operating system views each processor core as a separate processor
  • A multi-core processor typically increases overall performance of computer system

Registers

  • A processor contains small, high-speed storage locations
    • These storage locations are called registers
  • Registers are used during program execution
  • They temporarily hold instructions, data, or intermediate results of

calculations

  • The size of these registers is 2 or 4 or 8 bytes
  • The large sizes of registers increase the performance of CPU
  • For example, a computer having 32-bit (4-bytes) registers means CPU can

process four bytes of data at a time

  • A processor has different types of registers
  • Each register is used for a specific purpose

Machine Cycle

  • Process by which CPU obtains a program instruction from memory, decodes &

executes it, and stores result in memory (if necessary)

  • Also known as instruction cycle
  • CPU performs four basic operations to take action on each instruction of

program

  • These operations are fetching, decoding, executing, and storing (if necessary)

System Clock

  • System clock is an electronic component
  • It controls the timing of all operations of computer
  • It generates regular electronic pulses or ticks
  • It is just like your heart that beats at a regular rate to keep your body functioning
    • It is because computer clock is known as heart of the computer
  • It controls functions of computer by generating regular electronic pulses or ticks
  • System clock can generate pulses/ticks from millions to billions per second
    • Each tick or pulse is known as clock cycle
  • Clock speed is measured by number of clock cycles or ticks per second
  • A processor of PC can execute more than one instruction per clock cycle
  • For example, today PCs have clock speeds up to GHz (Gigahertz, where Giga means billion, and unit of cycle per second is hertz)
  • Thus, one gigahertz is equal to one billion cycles or ticks per second
  • Speed of processor depends upon clock speed
  • A processor can execute many instructions per second if clock speed is faster
  • Today, speed of PCs is up to 3 GHz or more
  • Speed of system clock affects performance of computer
  • However, speed of system clock does not affect performance of input/output devices and storage devices

Data Representation

Chapter 2 - Components of the System Unit

Data Representation

  • Data and instructions must be converted into binary form
  • Representation of data and instructions in binary form is called a coding

scheme

  • In coding scheme, every character, symbol, or numeric digit is represented by

a group of bits

  • Data and instructions can be converted into the binary form using different

coding schemes

  • Most widely used coding scheme is ASCII (American Standard Code for

Information and Interchange)

  • In 8-bit ASCII code, 256 characters can be represented
  • For example, in ASCII coding scheme, alphabetic letter โ€˜Aโ€™ (lowercase

uppercase letter) is represented as โ€˜01000001โ€™, while โ€˜aโ€™ (lowercase letter) is

represented as โ€˜01100001โ€™

Memory Unit

Chapter 2 - Components of the System Unit

Memory Unit

Structure of Main Memory

  • Main memory used in a modern computer is built in the form of a chip
  • Chip is made of semiconductor material
  • Main memory of a computer consists of thousands or millions of cells
  • Each cell can store a bit (Binary digit)
  • A bit represents 0 or 1
  • These cells are logically organized into a group of 8 bits called a byte
  • A byte is the basic storage unit in memory
  • When instructions of program and data are transferred to memory from a

storage device (i.e. hard disk), instructions and data exist in memory as bytes

  • Each byte exists temporarily in a specific memory location that has an address
  • The address is a unique number that identifies the location of a byte in

memory

Memory Unit Memory Access Time

  • The amount of time required by a processor to read data or instruction from memory is called access time
  • Usually, access time is measured in nanoseconds (ns)
    • A nanosecond is one-billionth of a second
  • Some manufacturers state access time in megahertz (MHz)
  • Access time affects overall performance of the computer
  • Control unit can access any byte of data from main memory by specifying its address
  • Different bytes from main memory can be accessed directly (or randomly)
  • Accessing any part of memory takes an equal amount of time
  • It is very fast as compared to other storage devices such as hard disk and an optical disk
  • For example, accessing data from main memory is more than 200,000 times faster than accessing data from the hard disk - It is because; main memory does not involve any mechanical movement in accessing data or instruction.