Structure of the Lesson
5.1 Learning Objectives
5.2 Introduction
5.3 Hardware Components
5.3.1 Motherboard
5.3.2 Processor
5.3.3 Power supply
5.3.4 Cabinet
5.3.5 Memory (RAM)
5.3.6 Hard disk
5.3.7Optical Disk Drive
5.3.8 Keyboard and mouse
5.3.9 Monitor (display)
5.3.10Video card and sound card
5.3.11 Speakers and headphones
5.3.12 Modem
5.4 Software component of computer
5.4.1 Operating systems
5.4.2 Application software
5.4.3 Graphics softwares
5.4.4 Drivers
5.4.5 Screen Savers
5.4.6 Antivirus softwares
5.4.7 Server softwares
5.5 Summary
5.6 Glossary
5.7 Suggested Answers to SAQ
5.8 References/Bibliography
5.9 Suggested Readings
5.10 Model Questions
5.1 Objectives
The objective of this chapter is to provide the information and
knowledge about the components of a computer system. The major components of
the system are hardware and software. When we want to purchase a new computer,
as beginners only one question is in our mind that which computer should be
purchase and which software should be installed in our computer. This chapter
will elaborate the information about the computer and the essential components
of the computer like motherboard, microprocessor, RAM, Hard disk, Optical disk
drive etc. Further this chapter will elaborate the software and its types.
5.2 Introduction
Normally, The word
computer is abbreviated as PC. The personal Computer is simple as well as
complicated. Simple in the sense that computer is assembled simply by plugging
of various components with in the fraction of time. No special skill and
special knowledge is required. Even a fifth class student can assemble a
computer with some training. This is possible due to advancement of technology
because technology has developed such components, which areintegrated easily
with other hardware. Now computer is
complex due to advancement and facilitation of integration the structure of
each part has become complex. Normally component of computer system is termed
as hardware components but I must quote here that software is also a basic and
necessary component of computer system.
5.3 Hardware component of computer system
The hardware components
and the peripherals necessary to assemble a personal computer are given below
5.3.1 Motherboard
This is the basic
circuit board and first component to fit into the cabinet to start assembling. This board is the core of the system. Every
other component is attached to this board for integration. It contains the
connectors to attach microprocessor, BIOS, RAM, Hard disk and also expansion
slots to connect other devices like optical drive, floppy disk drive, Keyboard,
mouse, display device or printers. Traditional motherboard does have specific
slot for each I/O device like keyboard have special slot on the motherboard and
similarly mouse and printer do have their special ports on motherboard. But
after the invention USB every slot has been swapped with one Slot called USB
port. Modern motherboard has inbuilt modem and LAN card for Internet
connectivity of the computer.
MOTHERBOARD
5.3.2 Microprocessor
It is also called CPU
(Central processing Unit) of the computer. It is a chip or IC (Integrated
circuit). The main function of microprocessor is to execute the instruction
stored in memory and also stored the results in memory once again.
Microprocessor posses its own memory called cache memory to enhance the
processing speed of the processor. It is the device which is responsible to
quote the speed of your PC. How fast is your PC? Answer of this question is
configuration of microprocessor of your PC.
Microprocessor can under stand only machine language. So instruction
given to the microprocessor should be in Machine language. Main companywhich
manufacturesmicroprocessors is Intel. Intel introduced its first microprocessor
in 1971 named as 4-bit microprocessor 4004 and its 8-bit microprocessor 8008 in
1972. The 4-bit and 8-bit microprocessor means that the processor can execute
the instructions having size of 4 bits or 8 bits. Larger the instruction size
greater the speed. With the advancement in technology 16-bit, 32-bit microprocessor
is available in market. Now, in modern personal computer we are using 64-bit
microprocessor. More popular models of microprocessor for personal computers are Dual core, Intel core i series like i3,i5,i7 etc.
5.3.3 Power supply
Power supply is an
electrical device responsible to supply the power to eachdevice which is
integrated with motherboard. Every integrated device hastwo connections one is
connected with motherboard and other with power supply. Power supply is plugged
with outlet of 220V. Its main function is to control the voltage and supply to
other device as per their requirement. So power supply has internal fuse which
give the protection to other devices from fluctuation of voltage. It is also
called SMPS (Switch Mode Power Supply).
POWER SUPPLY
5.3.4 Cabinet
This is a box thatcontainsthe
all the components of Personal computer into single unit. All the physical
components of computer are fitted in this frame. This frame is fitted with
power supply and the other devices like motherboard, hard disk, RAM, optical
disk drive can be fit in this frame by tightening of the screws. There are four
types of computer cabinet
TOWER CASE
DESKTOP CASE
DESKTOP CASE
PORTABLE CASE
ALL IN ONE CASE
ALL IN ONE CASE
5.3.5 RAM
Full form of RAM is RandomAccess Memory which is known by
different names such as internal memory,
physical memory, main memory, temporary memory, volatile memory. This memory is
the main part of the computer system. This is temporary memory. It stores the
data temporarily, when we switch off the computer the data stored in this
memory is lost. This memory is used to
store programs for processor. Any
program or set of instruction, which is to be executed by the processor, is
first stored in this memory and then it is executed by processor. Further the processor
once again stores the result of execution in this memory. It is just like a
serving plate on which we store the instruction and serve to the processor. Its
capacity is measured in Mega bytes, Giga Bytes. Bigger the size of RAM more
will be the speed of computer. Because
processor is designed to execute 1012 instruction in seconds. These
instruction are served in the RAM . If size of the RAM is not large enough, the
processor has to wait for instructions to be served. This will keep the CPU idle
and freewhich slows down the speed of computer system.
RAM
5.3.6 Hard Disk
Hard Disk is also called
secondary storage device or permanent storage device or HDD (Hard disk drive).
This component of computer is called memory of computer. It stores the data
permanently. The data stored in this device will remain for ever until we
delete it or damage the device. Now various techniques have been developed to
recover the data from damaged hard disk. The capacity of hard disk is measure
in Giga Bytes or Tera Bytes. To delete
the whole data of this device we often use the term format. Formatting is a
technique to clear all the data stored in secondary storage device. However formatting
not only clears the storage device but it also stores the file system into
device.
5.3.7Optical Disk Drive
Optical disk drive is
a disk drive by which we can store data
on optical disk. Optical term is related with light. Optical disk is disk which
uses light to store data Some optical disks are readable like CD ROM i.e. compact disk read only
memory. Some are writable like CD RW
compact disk writeable. DVD is another class of optical disk with larger
capacity the CD. Now these days this disk has taken place of conventional
magnetic tape. Due to its compact size, cheap price and large storage capacity it
has becomes a popular portable storage device.
5.3.8 Keyboard and mouse
They are the most
important input devices of PC. Everyone is familiar with this device but most
of us are not aware about somebasic factsof these components. A standardkeyboard has 101 keys. With this
conventional keyboard, another type of keyboard is also available for use i.e.
Software keyboard, which is displayed on the screen. This keyboard is part of the operating system. To display this keyboard
on the screen, Click on START >> RUN>> type OSK , you will get this
keyboard. On screen keyboard is shown in figure below.
Yet another type of
keyboard is the projection keyboard. This type of keyboard projects the laser
image of keyboard on flat surface. An infrared sensor senses the movement of finger
in the projection and type accordingly.
Mouse
A pointing device used to select the command
on the screen. Before the invention of windows we had command-based operating
systems called DOS. In this operating system, we had to type commands to any
operation, for example simply to copy, a file we had to type command and file
names to instruct computer to perform job. However this changed when GUI
operating system came in to existence. Then usage of mouse became popular.
Different types of mouse are in the market like MechanicalMouse, Optical Mouse,
USB Mouse and Wireless Mouse etc.
MOUSE
5.3.9 Monitor
A display Device used for output. Monitors are
very familiar devices. We also call this
device as CRT (cathode Ray tube) or LCD (liquid crystaldisplay). It resembles
the television screen. The monitor is allied with keyboard. What ever we type
on the keyboard it displays on the screen. This terminal consists of a small memory
known as buffer. The size of memory or buffer is very less;it simply stores the
number of character that can be displayed on the screen. Each character enteredthrough
the keyboard is stored in the buffer and from buffer it is displayed on the screen.
A small vertical bar keeps on blinking on the screen, which is called cursor,
and it, states the current position. This display device provides the instant
display of operation and it is totally silent in its operation.
5.3.10 Video card and sound card
Video card is additional
device which is not present in normal PC. This is hardware device which we have
to add in the our PC as per requirement. Basically, sound card is meant for
converting analog video signals in to digital format. These cards are
responsible for conversion of analog video signal into digital format. These
are the interface between the analog cameras and PC. It may be in the form of expansion card (i.e.
itcan be mounted on the motherboard expansion slot) which inbuilt on the motherboard as chipset. Now these days, digital cameras are
available in the market, which directly captures the video or image in digital
format, and you can transfer this video or image directly into your PC, no video card is required for such
digital devices.
5.3.11 Speakers and Head phones
These are familiar terms
for us. In our PC, Sound data is digital
(e.g. mp3 files). There are certain software (like media player, VLC etc.) which convert the digital data in to relevant sound signals. These
voice signals can heard through speakers or head phones.
Headphones
5.3.12 Modem
The modem is derived
form the words modulate and demodulate. A modem is both modulator and
demodulator so it is called a modem. The function of modem is to convert analog
signal in to digital one and the process is called modulation, and digital
signal to analog one and process is called demodulation. This device is related
connectedInternet and attached with PC. The main function of Internet is connected
with telephone lines. Whenever we need anInternet connection for our PC, we find
telecommunication companies inmarket which are providing these services. Data
travels in Internet through telephone lines. Through these telephone lines only analog
signal can be transferred. But our PC is digital and generates digital signals
so modem plays role to convert digital signal to analog signal to transfer to
telephone lines.
5.4 Software component of computer
Computer cannot do
anything on its own. It must be directed or instructed to do a desired job.
Hardware are just a lifeless devices, they cannot perform any functions without
instructions. So Software is sequences of instruction given to hardware to
perform specific job. The instructions are written by expert professionals,
tested, integrated and released in market for sale. These instructions are
written in a language which is understandable by computer. It is software that
controls the activity of processing by the computer and the computer performs
what the software wants it to do. The
instructions written for the hardware in a set called programs or computer
programs. The group of these programs is called software. In clear-cut way,software can be defined as a collection of programs
whose objectives are to boost the capabilities of the hardware machine. Types
of software necessary for the functioning of PC are given below.
5.4.1 Operating systems
OperatingSystem (OS) is
a set of programs to control the operation of computer system. OS belongs to
system software category. This software is basic and essential for PC. When we
buy PC, the first software, which we should install into PC, is Operating
system. It is just like a governmentfor the entire hardware.
It manages the whole
hardware and its functioning. It is a system software to manage the resources
of computer system such as memory, processor, input , output and data. This
system software has different modules to manage the different hardware like CPU
scheduler tocontrol and manage the working of CPU, Memory manager to manage and
control the functioning of main memory i.e. RAM. Operating system is further classified in to
following types.
·
Multiprocessing: It controls and manages the CPU to process
multiple jobs at same time
·
Multitasking: It manage the CPU to run more than one programs of a
job at the same instant.
·
Multithreading: It controls the CPU to run different parts of one
program concurrently.
·
Multi-user: It controls the CPU to allow more than one user to
user Computer at the same time.
5.4.2 Application software
These types of software
are application oriented. These are developed for particular application. They
are also known as application package. For example, Banking software is
application software is designed for
banking jobs like management of accounts and their transactions etc. Similarly,
a program writtenby a programmer for gaming is also called application
software. The software belonging to this category are, Games, word processing
software like MS Word, WordPad, Acrobat Reader, MS PowerPoint, MS Excel, and
other software which are used by many business organization for their
management like shopping mall management, Inventory management etc.
5.4.3 Graphics software
These types of software are used for graphic works. We classify the graphics as 2D
graphics, 3D graphics and video editing
software. 2D graphics is further
classified as Raster graphics and vector graphics software.
2D Graphics software:
2D graphics software also called image editing
software. Thesesoftware are used to edit and draw the new images. These
software are classified into two distinct categories as below:
·
Raster Graphics software:These software operate
on raster images or graphics. In raster graphics, images or graphics consist of
pixels. The basic element of this graphic is pixel. Pixel as we have already
studied a tiny particle on the screen. Group of pixel define the resolution of
the screen. Some important graphics software commercially in use are Adobe
Photoshop, Adobe Photoshop Light Room, Adobe Photoshop Elements, Corel Painter,
MS Paint etc. Some free raster graphic software available on net are Paint.Net,
Picasa, Artweaver, Pixia etc.
·
Vector graphics software:Thesesoftware are used
to edit vector graphics. In Vector graphics is, animage or a
graphic consistsof lines and vectors. Some vector graphics software areCorelDraw,
Adobe Ilustrator, Micromedia freehand, Dia etc.
·
3D Graphics software: 3D software uses the
three dimensional data of the scene of the image for processing. These software
are used for the purpose of performing rendering, generating wire frame model,
3D Models and 3D printing. This software are highly in demand in engineering,
health care and entertainment industries. Some common software of 3D graphics are
Autodesk Maya, Autodesk 3D’s Max, Maxon Cinema 4D etc.
·
Video editing software:Video editing is
another computer graphic branch which
widely uses some video editing softwarelike Blender VSE, LiVES, VirtualDubMod
etc. Some freely available video editing software includes Adobe Premier
Express, Window Movie Maker etc.
5.4.4 Drivers
Device driverisa type of
special software. Drivers are actually hardware dependent software. They
operate or control a particular type of hardware, which is attached with
computer. Hardware like Keyboard, mouse has his owndrivers, which are already
packed along with operating system. Even monitor has its own drivers, whichare
also packed within operating system. Attached hardware cannot function without
its driver. A Driver communicates with
its hardware and provides the interface between hardware and computer system.
If we try to attach a new printer with computer for taking printout, we must
first install printer driversin thecomputer. Whenever we purchase new hardware
to attach with computer, we also get its driver CD with it. Drivers are the system software and need
expertise to develop. Only expert hardware programmer can develop these types
of software.
5.4.5 Screen Savers
Screen saver is a
computer program or software that blackens the screen or displays moving images
when computer is not in use for a particular period of time. As the name
suggests, they are designed to save the display screen. Before the invention of
LCD, CRT was used as display device.
From inside, CRT screen is made up of phosphorus coating. To display an
image, the phosphorus coating is projected with light beam. If the screen remains
idle for long time, the phosphorus area burns up the screen with permanent
shadows or dot and damages the screen. So this software automatically changes
the screen with moving images or animations after a specific period of time incase
the screen remain idle. Now LCD does not have this type of problem. In fact,
screen saver are used for entertainment purpose these days. These software are widely used in public such
as ATM, railway Information machines. The risk of burningishigh the CRT of
these machines, if thy remain in standby mode or idle period of time.
5.4.6 Antivirus software
We all are familiar with
word computervirus; Computer virus is a software or set of instructions or
program to malfunction the computer system. We already havestudiedthat a computer
does not have common sense.Computer just executes the instructions, whicharegiven
to it. Virus software are intentionally designed and developed to cause failure
inthe computer system. This software are
served secretly with the free entertainment software like games, screen savers
etc. from internet. When download we
entertainment software, these viruses get installed in our computer system
secretly without our knowledge and get executed and malfunction our computer
system. Different classifications of
virus are -
- Malware:
It is virus program that delete the important system file of the operating
system.
- Computer
worms: This program attack on
secondary memory and replicate the data stored in hard disk again and
again.
- Trojan
Horses: This program enters in our
computer with normal data and start deleting our important data and files
- Spyware:This
program remains in our computer and send the key hits (like password typed
etc.) and screenshot of computer screen to attacker by email.
Lot of Antivirus
software is there. This software is used to prevent, detect and remove the
computer viruses. Antivirus software is installed in computerand becomes the
security guard of computer. They scan every data, which is to be copied in to
computer system.
5.4.7 Server software
As name suggest server isa
software that means to serve or a component to provide services. Server
software responds to the request of providing services. These software runs on
dedicated computer. Servers are computer program meant to serve the requests of
other programs called clients. Server performs some task on behalf of
clients. Typical computing servers are-
·
Database server: This server software provides database to the
computers, for example oracle server, MS SQL server etc.
·
File Server: It provides access to remote files and file sharing
with remote computers.
·
Application server: This server is committed to run software
applications.
·
Sound Server: This server provides multimedia (Image , Video)
broadcasting.
·
Game servers: Servers the video games to client on request.
·
Mail Server: Responsible to
handle sending and receiving of emails.
·
Proxy Server: This server act as intermediate between client and
other busy servers.
·
Web Server: This server is dedicated to provide HTTP(Hyper Text
Transfer Protocol) services to client, for example IIS server, Personal web
server, Glass Fish Server etc.
5.4.8 Programming Languages
Program is a set of
instruction given to computer to perform particular task. The language in which
these instruction are written for computer is called programming languages.
Question arises that computer can understand only machine language so program
should be written in machine language and there should only be one programming
language i.e. machine language. This question is quite correct and has good
logic. Machine language is very tough language. This language is difficult to
learn and program. Program written in this language is difficult to test and
modify. Expert programmer is required for programming in machine language. I
was conceptualized during second generation of computers that programming
language should be easy and human like language and high-level language came
into existence. A concept of translator software has been introduced which
translates the program written in high level language into machine language. At
present there are over 200 programming languages in market like java, c, c++
etc.
5.5 Summary
Computer system is based
on two components i.e. hardware and software. With the advancement of
technology,lot of different types of hardware is available in market. In this our
chapter aim was to explain the basic hardware and software components, the
common components, which we use in daily computing. In a computer system the
common about components, which we often use are term processor, memory, mouse,
software, virus antivirus etc. Although most of us have heard these terms, yet
many of us have remained unaware about the functioning and types of these
terms. After reading this chapter reader, we will realize the meaning of each
term used in the computer system
5.6 Glossary
BIOS Basic Input/Output System
RAM Random Access Memory
CPU Central Processing Unit
USB Universal Serial Bus
I/O Input or output
HDD Hard Disk Drive
DOS Disc Operating System
HTTP Hyper Text Transfer protocol
Machine Language A
hardware language used for hardware programming.
EBCDIC Extended Binary Coded Decimal Interchange Code
MB Megabyte
TB Terabyte
CD Compact Disk
DVD Digital video Disk
LCD Liquid Crystal Display
CRT Cathode
Ray Tube
TCP Transmission Control Protocol
IP Internet
Protocol
VIRUS Vicious Internal
Rabbit/Rodent Uprooting Stuff
WWW World
Wide Web
WAIS Wide
Area Information Servers
ZIPOS Operating System
ISO International Standards
Organization
HTML HyperText Markup Language
FTP File Transfer Protocol
ASP Active Server Pages
5.7 Suggested Answers to SAQ
Que:What is the function of CPU ?
The brain of computer is
called CPU (Central processing Unit) of
the computer. It is a chip or IC (Integrated circuit). The main function of CPU
is to execute the instruction stored in memory and also store the result in the
memory. CPU possesses its own memory called cache memory to enhance the
processing speed of the processor.
Que:
Explain the functioning of power supply in computer system?
Power supply is an
electrical device responsible to supply the power to each device which is
integrated with motherboard. Every integrated device has two connections one is
connected with motherboard and other with power supply. Power supply is plugged
with outlet of 220V. Its main function is to control the voltage and supply to
other device as per their requirement. So power supply has internal fuse which
give the protection to other devices from fluctuation of voltage.
Que:
Why more memory is required for more speed of a computer system?
RAM is used to store
program for processor. Any program or
set of instruction which is to be executed by the processor is first stored in
this memory and then it is executed by processor and again processor store the
result of execution in this memory. It is just like a serving plate on which we
store the instruction and serve to the processor. Its capacity is measured in
Mega bytes, Giga Bytes. Bigger the size of RAM more will be the speed of
computer because processor is designed to execute 1012 instructions in seconds. These instructions
are served in the RAM. If size of the RAM is not large enough, then processor
has to wait for instruction to be served. This will keep the CPU idly which
slows down the speed of computer system
Que : Give the classification of operating system?
Operating system is
further classified in to following types.
·
Multiprocessing: It control and manage the CPU to process multiple
job at the same time
·
Multitasking: It manages the CPU to run more than one program of a
job at the same time.
·
Multithreading: It controls the CPU to run different part of a
program concurrently
·
Multi-user: It controls the CPU to allow more than one user to use
computer at the same time.
Que: State and explain the different classification
of viruses?
Different
classifications of virus are
·
Malware: It is virus program that deletes the important system
file of the operating system.
·
Computer worms: This program attacks on secondary memory and
replicates the data stored in hard disk again and again.
·
Trojan Horses: This program enters in our computer with normal
data and starts deleting our important data and files.
·
Spyware: This program remains in our computer and sends the key
hits (like password typed etc) and screenshot of computer screen to attacker by
email.
Que: Name the different types of software servers?
Typical Software servers
are
·
Database server: This server software provides database to the
computers, for example oracle server, MS SQL server etc.
·
File Server: It provides access to remote file and file sharing
with remote computers.
·
Application server: This server is committed to run software
applications.
·
Sound Server: This server provides multimedia (Image , Video)
broadcasting.
·
Game server: Serves the video games to client on request.
·
Mail Server: Responsible to
handling for sending and receiving of emails.
·
Proxy Server: This server act as intermediate between client and
other busy server.
·
Web Server: This server is dedicated to provide HTTP(Hyper Text
Transfer Protocol) services to client, for example IIS server, Personal web
server, Glass Fish Server etc
5.8 References/Bibliography
·
Digital Computer Fundamentals By Bartee
·
Discovering Computers 2009: Brief by Gary Shelly, Misty Vermaat
·
Fix Your Own PC By Corey Sandler
·
Foundations of Information Technology By D. S. Yadav
·
IBM Corporation (1975). Introduction to IBM Direct-Access Storage
Devices and and Organization Methods
·
IBM Systems Magazine Jim Utsler
·
Introduction To Computers (Sie)By Norton
·
Introduction to Information Technology By I. T. L. Education
Solutions Limited, Itl
·
JCL Programming Bible (with z/OS)
·
Microprocessor-based Control Systems.Sinha, Naresh Kumar.
5.9 Suggested Readings
·
Computer Fundamentals and Programming in C By J. B. Dixit
·
Origins and successors of the Compact disc: Contributions of
Philips to Optical storage by Hans Peek, Jan Bergmans, Jos van Haaren, Frank
toolenaar and Sorin Stan.
·
Fundamentals of Information Systems By Ralph Stair, George
Reynolds
5.10 Model Questions
Que: Explain the various
types of keyboards ?
Que: What are device
drivers?
Que: What is difference
between system software and application software?
Que: What is difference
between Malware and Spyware?
Que: Explain the various software servers?
Que: Write the working of Motherboard?
Que: Explain the use of headphones?
Structure
of the Lesson
6.1 Learning Objectives
6.2 Introduction
6.3 Basic Computer Operations
6.4 Basic Architecture of Computer system
6.4.1 Input unit
6.4.2 Output Unit
6.4.3 Storage Unit
6.4.4 Arithmetic Logic Unit
6.4.5 Control Unit
6.5 Various parts of CPU and their Significance
6.5.1 Arithmetic Logic Unit
6.5.2 Control Unit
6.5.3 Registers
6.5.4 BUS
6.6 Instruction Execution Cycle
6.7 Summary
6.8 Glossary
6.9 Suggested Answer to SAQ
6.10 References/Bibliography
6.11 Suggested readings
6.12 Model Questions
6.1 Objectives
The objective of this lesson is to
understand the basic operations of computer like input output, processing,
storing and controlling and how these operations are performed to execute a
job? This chapter will also explain the basic architectural unit of computer.
The function of each unit is also described in this lesson. Detailed knowledge about the interaction of
instruction and data and processing of data is also explained in this chapter.
The significance of each part of control unit is also discussed in the chapter.
Various types registers and their function during execution of instruction will
also be discussed in this chapter. At the end reader will have knowledge about the
various functional units of the computer and its role in execution of instruction. Reader will be enlightened with the
interaction of each unit with other during the execution of instruction.
6.2 Introduction
With the advancement of technology
computer has made implausible improvement. We have already studied in the
chapter of computer generation, the size of computer has decreased and
computational power has increased during the evolution of technology. In this
race the internal design of the computer has become complex. Advancement in
technology has become a challenge for the computer designers. This challenge is in every aspect like set
design, logic design and functional organization. While thinking all this, a
question may arise in minds that what is the basic architecture and organization
of computer. Before answer to this
question I would like to explain the basic operation of a computer
6.3 Basic
Computer Operations
All computer systems perform five
basic operations for converting raw data into useful information and presenting
it to user.
Basic Operations
|
Hardware involved
|
Inputting
The process of entering data into computer system |
Keyboard, Mouse, Microphone
|
Processing
Performing arithmetical and
logical operations on input data in order to convert into useful information
|
Motherboard,
CPU, RAM (Main Memory) |
Storing
Saving data and instruction so that they are available for processing as and when required. |
Primary Storage:
RAM (Main Memory)
Secondary Storage:
Hard disk, Floppy disk, CD ROM, Magnetic Tape |
Output
The process of producing useful information to the user as a hard copy or soft copy |
Monitor,
Printer, Speakers, |
Controlling
Directing the manner and sequence
in which all of the above operation are performed.
|
Circuits, Control Buses
|
Basic
operations of Computer system
The architecture of computer deals
with the general organization and interconnection in the computer. The internal
architectural design of computers differs from one system model to another.
However, the basic organization remains the same for all computer system. The
Personal computer we are using these days are called VON NEUMANN (Vonn Neumann
was a mathematician and physicist who designed the computer architecture in
1945) computers due to their main architectural design. Microprocessor, I/O and
memory as interconnected just as NEUMANN suggested. Today we have great
variation in basic building blocks of the computer at hardware level but the
design level tier meaning is still the same .
The high level design of computer is given below
Basic architecture of Computer
system
In high level design of computer has three main parts
●
Central processing unit: CPU is
brain of computer responsible for all computation, control and management.
●
Memory: It stores program and data
and instruction for computer. It is like a serving tray of CPU. Memory also has
the responsibility to store results computed by CPU.
●
I/O: The interface through which we
can store the data and instruction into memory for execution and serve the
result from memory to user.
Design of computer is like human
body. We have CPU i.e. our brain responsible for all processing and
calculations for taking decisions. Neverous system controlled by brain to
control the whole body part and to provide interaction between them. Human body
also has memory used to store data and instructions. I/O devices in human body
are eyes, nose, ears and mouth through these organs we can receive data and
instructions and stores in memory. Our brain process these instruction and data
from memory and generate the results.
On basis of above design the basic organization of computer
is said to consist of five interconnected units as shown in figure.
Block Diagram of Computer
6.4.1 Input unit
For Computation, we have to enter
data and instructions to computer system. The input unit that connects the
external environment with computer system performs this task. This unit is the
interface between user and computer system. Data and instructions given to
computer must be in computer language, i.e. the language that is understandable
by computer. Computer knows only binary language. So it is the responsibility
of input unit to transform the data and
instructions in binary codes before storing it into primary memory. Input unit
accomplishes this transformation.
Technologically, these devices are designed in such a way to fulfill the
requirement of computer system. From above discussion the basic functions performed
by input unit are-
●
It reads the data and instructions
from user.
●
Converts these instruction and data
in computer understandable language
●
And store the converted data and
instructions in computer memory for further processing
6.4.2 Output Unit
Output unit has reverse job form
input unit. The main responsibility of output unit is to display or to print
the result of computation to user in human understandable language. Output unit
links the computer with the external environment. CPU works on binary code and
also generates results in binary forms. Before supplying the result to user, it
must be converted to human readable language. This task is accomplished by
output devices. Technologically, output devices are designed in such a way to
fulfill the requirements of computer system. From above discussion, the basic
functions performed by output unit.
●
It accepts the results produces by
the CPU from memory which are coded in computer language (i.e.
binary language)
●
Converts these results into human
understandable language
●
And supplies these results to the
user.
6.4.3 Storage Unit
The human storage unit is memory and
is controlled by the brain. Similarly, storage unit of computer is controlled
by control unit. Storage unit of computer is memory where data is registered.
This unit is responsible for storing data, intermediate results of calculations
and gives final result for output. This unit is also responsible to store input
data for CPU to perform calculations. Following are the basic function of
storage unit.
●
This unit stores data given by the
user for calculation and instruction to be executed on that data. This unit is
like a serving tray for CPU.
●
It also stores the intermediate
result given by the CPU while processing.
●
This unit is also responsible to
store the final result of computation for output.
6.4.4 Arithmetic Logic Unit
This unit is responsible for
Arithmetical and logical processing of data. This unit receives Instruction and
data from storage unit and executes the data as per given instructions. During
the execution of instruction, it performs operations such as addition,
subtraction, multiplication, comparison and other Boolean operations. It is a
high speed digital circuit that performs the calculation and does
comparisons. No processing is done in
storage unit. Intermediate results generated in the ALU are temporarily
transferred back to the primary storage until the final the calculation
completed. The data may move to and from ALU to primary storage file till the
processing is over. After the completion of processing the final result are
transferred to storage unit for output.
6.4.5 CONTROL UNIT
This unit is like the nervous system
of the computer and major Components of CPU. The communication between each
unit while processing or execution of data is controlled by control unit. This
unit is responsible to maintain order and manage the operation and also
coordinate the entire system. This unit commands the other unit in the form of
signal to process their job to complete the execution. This unit fetch the
instruction from storage unit and passes it to ALU and issue the signal to it,
when processing is the done by ALU. Then control unit again issues the signal
to storage unit to store the result given by ALU. When storage gets completed
then it again issues the signal to Output unit to display the result to output
device.
6.5 Various parts of CPU and their Significance
The Central processing unit is the
brain of computer system. It has following o main parts.
●
Arithmetical and logical Unit.
●
Control Unit
●
Registers
●
Buses
We
are familiar with terms control unit and ALU.
Also we have and already studied the functioning of these parts. The CPU
is circuitry of a microcomputer called microprocessor. The parts of the CPU are
usually connected by a Circuit referred as a bus, which act as a communication
link between the various parts of CPU to send signals, data and instruction.
Control unit of the CPU does not execute instructions, it controls the other
parts of the systems to execute the instructions. It control the movement of
electronic signals between the main memory and ALU and also the control signal
between the main memory and input output devices.
ALU perform all the arithmetical and
logical processing like addition, Subtraction, multiplication, Comparisons
(greater then, less than equal to etc).
● REGISTERS
Registers are memory of CPU. It is
special temporary storage location with in the CPU. This storage memory is fast
enough to store or fetch the data and instructions. This storage is fast as
compare to RAM and hard disk But the storage capacity of registers are very
small i.e. in bits. Registers are responsible to accept, store and transfer
data and instruction when they are command to do so. To execute an instruction,
microprocessor receive instruction from main memory and stores it into
register. The number and types of registers in a CPU vary according to the CPU
design. The size and numbers of registers affect the processing power of the
CPU. The size of registers may be 8-bits, 16-bits, 32-bits, 64-bits. Larger the
size of register a CPU more will be the processing power of CPU. Now, these
days, we are using 32-bits or 64 bits CPU in personal computers. The 8-bits and
16-bits CPU are being used in car, refrigerators etc. We can differentiae
registers in following types according to their use and functioning.
i.
General purpose registers
ii.
Program Counter
iii.
Instruction register
i.
General purpose
registers
●
Accumulator-:
This is very important register and it stores the result of arithmetic and
logical operations of CPU. An accumulator is a register in a computer’s central
processing unit (CPU) that stores mathematical information, such as additions,
subtractions, etc. For example, when adding a list of numbers, each number is
entered into the accumulator and added together. Once all numbers have been
inputted into the accumulator, they are stored on the computer in the register.
Without an accumulator, each calculation would have to be inputted manually.
●
Memory address register-:
It stores the address of main memory location from where the data is to be
fetched for execution and also the address of location where the result is to
be stored after execution.
●
Memory Buffer Register-:
It contains a copy of the designated memory location specified by the MAR after
fetching or storing the contents of the memory location.
ii. Program
Counter: - This register is also called
Instruction counter. This register stores the memory address of the instruction
to be fetched for execution.
iii. Instruction
register-: This register actually stores the
fetched instruction for execution and whose address is in instruction counter.
●
Bus
Bus is the electronic path way
through which bits are transmitted as signals between the various components of
computer. Depending on the design of system, several types of buses are in
existence. They are classified by name according to its function.
i.
Control bus.
ii.
Address bus.
iii.
Data bus.
i. Control Bus:-This bus has responsibility of all timing and controlling
function sent by the control unit to other units of the system.
ii. Address:-This
bus locates the storage position in memory from where the next instruction or
data will be found for execution.
iii. Data bus-: This is the most important bus. This bus carries data
throughout the CPU. This is the path way where the actual data transfer takes
place. The three buses paths are shown in figure.
6.6
Instruction Execution Cycle
To execute instruction CPU goes
through two basic cycles.
●
Instruction Cycle:-During
this cycle two main operations has taken place.
a)
Fetch:-This
operation fetches or brings the instruction from main memory into the
registers.
b)
Decode:-Decoding
means interpretation of the instruction to decide which course of action is to
be taken for execution of the instruction and what sequence of control signals
must be generated for it.
●
Execution cycle:-During
this cycle the instruction is execution by the ALU and result is stored in the
Accumulator register. The program Counter is Incremented to identify the
location of the next instruction to be executed and this cycle goes on
repeating until the Program ends.
6.7 Summary
Computer is organized as a unit.
Each unit is responsible to perform the basic operation (like inputting,
outputting, storing, processing, controlling) of the computer. Input unit is responsible for inputting
operation with devices like keyboard mouse etc. Output unit is for outputting
operation with devices like monitor and printer. Similarly storage unit is
responsible for storing operation with hardware devices like RAM. The main unit is central processing unit
which combination of arithmetic and logical unit. This unit is brain of the
computer. ALU is responsible for arithmetic processing and logical processing.
Control unit job is to control the operation of all the units. This unit
basically coordinates the interaction of all the units. The CPU has registers
and buses. Registers are the memory unit for CPU to store the instructions and
address of instruction in memory for execution. We had studied various types of
registers and their basic operations. Buses are again important part of the
CPU. Buses are the circuit pathway to communicate the data, addresses and
control signal from all other units of the computer system.
6.8 Glossary
ALU Arithmetical
and logical unit
CU Control
Unit
CPU Central
Processing Unit
MAR Memory
Address Register
MBR Memory
Buffer Register
PC Program
Counter
IR Instruction
Counter
I/O Input
/ Output
RAM Random
Access Memory
6.9 Suggested Answers to SAQ
Question: What are the basic
operations of Computer?
Inputting:
The process of enter data into computer system.
Output: The process of
producing useful information to the user as a hard copy or soft copy.
Storing: Saving
data and instruction so that they available for processing as when required.
Processing:
Performing arithmetical and logical operations on inputted data in order to
convert into useful information.
Controlling: Directing the manner and sequence in which all of the above
operation are performed.
Question: What is basic function
Storage unit?
Following are the basic function of
storage unit-
●
This unit stores data given by the
user for calculation and instruction to be executed on that data. This unit is
like a serving tray for CPU.
●
It also stores the intermediate
result given by the CPU while processing.
●
This unit is also responsible to
store the final result of computation for output.
Question: Explain the Main parts of
CPU?
CPU has following main parts.
●
Arithmetical and logical Unit.
●
Control Unit
●
Registers
●
Buses
Question: Explain the various types
of Registers?
Following are the various types of
registers
●
General purpose registers
●
Program Counter
●
Instruction register
iv.
General purpose registers
●
Accumulator-: This is very important register and
it stores the result of arithmetic and logical operations of CPU.
●
Memory address register-: It stores the address of main memory
location from where the data is to be fetched for execution and also the
address of location where the result is to be stored after execution.
●
Memory Buffer Register-: It contains a copy of the
designated memory location specified by the MAR after fetching or storing the
content the memory location.
●
Program Counter
This register is also called
Instruction counter this register store the memory address of the instruction
to be fetched for execution.
●
Instruction register
This register actually stores the fetched instruction for
execution and whose address is in instruction counter.
Question: What is the main function
of control bus?
This bus has responsibility of all
timing and controlling function sent by the control unit to other units of the
system
.
6.10 References/Bibliography
● P.K Singh, Basics of computer
● Ralph Stair, George Reynolds,
Principles of Information Systems
● Stallings William, Computer
Organization & Architecture 7e
● Anita Goel, Computer Fundamentals
● Sivarama P. Dandamudi, Guide to RISC
Processors: For Programmers and Engineers
6.11 Suggested Reading
● P.K Singh, Basics of computer
● Anita Goel, Computer Fundamentals
6.12 Model Questions
● Differentiate the functioning of
data bus and address bus?
● What is the difference between MAR
and MBR?
● Explain how CPU executes a
instruction?
● Differentiate the functioning of
input unit and output unit?
