Introduction to computers MRS. SOWMYA JYOTHI

UNIT 1
INTRODUCTION TO
COMPUTER
MRS. SOWMYA JYOTHI,
ASSISTANT PROFESSOR, MANGALORE

The term computer is derived from the Latin word
compute, which means to calculate.
A computer is an electronic machine, devised for
performing calculations and controlling operations that can
be expressed either in logical or numerical terms.
In simple terms, a computer is an electronic device that
performs diverse operations with the help of instructions to
process the information in order to achieve the desired
results.
 An electronic device, operating under the control of
instructions stored in its own memory unit, that can
accept data, manipulate the data according to specified
rules, produce information from the processing, and store
the results for future use.
 A Computer may be defined as - An electronic machine
that can solve problems by accepting data performing
certain operations and presenting the results of those
operations under the direction of detailed step-by-step
instructions.

Data is a collection of facts, figures or statistics, which can be
processed to produce meaningful information.
Data on its own has no meaning.
Example:-
A number such as 02332 could be a register number of a student
or a hall ticket number of a student.
Information is processed data with definite meaning.
It represents the facts, figures or statistics which have been put
into meaningful and useful form. Information represents the
structured data
Data processing is the conversion of data into a more useful form.
That is, transmission of data into meaningful information is called
data processing

Characteristics of a Computer:-
1. Speed:- Computers are capable of carrying out the task
with enormous speed. Computers can perform arithmetic
operations and manipulate information at phenomenon
speeds.
The speed of a computer is closely related to the amount
of data it can process. It is measured as number of
instructions executed in one second.
Usually a computer can execute million instructions per
second(MIPS).
Today’s computers, according to their class, can perform
from 4 MIPS (Millions of instructions per second) to 100
MIPS.

Characteristics of Computer
2. Accuracy:- In spite of high speed, computers rarely make
mistakes and can accurately perform all kinds of complex
computations, thereby providing accurate as well as consistent
information or result.
Errors do occur in computer-based information systems, but
these errors are due to program logic error, erroneous data or
due to human errors.
3. Reliability:- Computers are well adapted to perform repetitive
tasks and never get tired of repetitive calculations. Computers
consistently provide the same accurate results under all
operating conditions.
4. Reduced Cost- The cost of the computers has dropped
drastically over the years, thus their use in organization is now
cost effective.

Characteristics of computer
5. Storage Capability:- Computers can store large volumes
of data and instantly retrieve / manipulate the stored data at
any time.
6. Versatility- Refers to the capacity to perform completely
different types of work. Computers are versatile in that they
can perform almost any task, provided they are given the
appropriate logical steps. Computers can be utilized to
perform different types of tasks. They can be used in
business, industry, communication and research.
7. Diligence: Computers are machines and that do not get
tired or ‘lose concentration’ like human beings. If a large
number of calculations say million calculations are to be
performed the resultant output will remain exactly the same
even if operations are repeated any number of times.

Components of the computer
1. Input unit: This unit accepts instructions and
data.
2. Output unit: This unit communicates the results
to the user.
3. Storage unit: This unit stores temporary and
final results.
4. Central Processing Unit (CPU): This unit
performs processing of instructions and data
inside the computer.

Functional Units of the
computer

The CPU has three components:
a) The Control Unit
b) The Arithmetic Logic Unit (ALU) and
c) The Memory Unit.

CPU – Central Processing Unit
The ALU and the CU of a computer system are jointly
known as the central processing unit.
CPU is the brain of any computer system.
It is just like brain that takes all major decisions,
makes all sorts of calculations and directs different
parts of the computer functions by activating and
controlling the operations.

a) Control Unit:
It controls the overall operation of the computer system. It
controls all the other units, directs them to operate in a
proper way and co-ordinates various operations performed.
It instructs the input device to transfer the data and
instructions to the main memory and then to the arithmetic
and logic unit (ALU). Then, it sends the processed result from
ALU to the memory unit for storage and transfers it to the
visual display unit or to the ' printer.

b) Arithmetic Logic Unit (ALU)
This unit performs two kinds of operations, the
arithmetic processing and logical processing.
In arithmetic processing it performs all mathematical
operations such as addition, subtraction, multiplication
and division.
In logical processing, it performs the relational and
logical operations such as comparing larger or smaller
values, true or false statements, etc.

c) Memory Unit
This unit holds the intermediate results during the
course of calculations and provides the data as and
when required.
This internal storage is also called primary memory or
main memory. This memory takes the data from an
input device and stores it until the computer is ready to
process it. It also stores processed data and
intermediate results.
When the processing is finished, it transfers the results
to an output device.

Memory unit
The function of memory is to receive, store and
deliver data or instructions.
2 types of memory devices are- primary and
secondary memory.
 Primary memory stores the data/program
during execution.
 Secondary memories are large, cheaper and
slower than primary memory. They are slower
than the primary memories and are usually used
to store archival information.

Input Unit
This is the process of entering data and programs in to the
computer system. Computer is an electronic machine
which takes as inputs raw data and performs some
processing giving out processed data. Therefore, the input
unit takes data from the user to the computer in an
organized manner for processing.
An input unit accepts user data or instructions in
machine readable from and places them in the main
memory.
Examples: Keyboard, Mouse, Scanner etc

Output Unit:
 Main function of output device is to receive information
from the CPU and present it to the use in the desired form.
The output device translates processed data from a
machine-coded form to a form that can be read and used
by the people.
The most common types of output devices are the monitor,
which resembles a television screen, and the printer, which
prints copy from the computer onto a paper, magnetic tape,
magnetic disk and floppy diskette.

Components of a Computer:
A Personal Computer is made up of multiple
physical components.
These can be broadly divided into 2 categories:
1. Computer Software
2. Computer Hardware

Computer Software:
Refers to a set of instructions that is given to the computer
to perform a specific task.
It is a general term used that describes collection of
programs, procedures and documentation that perform
some tasks on a computer system.
Software guides the hardware in performing its task. Its
divided into:
System Software, Programming Software & Application
Software.
Computer Hardware:
Refers to any physical component of computer.
For example: CPU, Monitor(VDU), Hard Disk, CD, Printer etc

Difference between Software and the Hardware:-
Software refers to a set of instructions that are
given to a computer to perform a specific task.
There are 2 major categories of software.
1. System software 2. Application software.
System software is made up of control programs such as
the operating system.
Application software is used to process data such as
inventory, payroll, spreadsheet, word processor etc
All the electrical and electronic parts of a computer
system such as cables, CPU, disk, tape, modem etc are
called as hardware.
Software tells the hardware how to process the data.

Comparison b/w hardware & software
Hardware Software
These are physical parts/components of
computer
These are logical parts of computer
Hardware is an electric device Software is just set of instruction or
programs.
Hardware are attached with the computer Software are installed in the computer
Major types are:
i) input devices
ii) output devices
Major types are :
i) O.S means System Software
ii) Packages means Application
software
Hardware process data Software manage data.
Hardware follows the instructions of
software
Software tells the hardware what to do

Computer Software
Software refers to a set of instructions given to the
computer to perform a specific task. There are 2
major categories of software. They are:-
1. System software
2. Application software
System software:- System software performs the
basic functions necessary to start and operate a
computer. It controls and monitors the various
activities and resources of a computer. System
software is easier and more efficient to use the computer.

Application software:-
Application software is designed to perform people-
related tasks such as payroll, inventory and sales analysis.
These are programs that meet specific computational
requirements of a certain class of users.
They are user friendly programs that permit the user to
specify the inputs in a either assembly or high level language
such as C, C++ and Java etc.
Examples for application software are Tally, MS word,
MS excel and MS PowerPoint etc.

Software—Can be categorized into
 System software
1. System Control Software
2. System Support Software
3. System Development Software
 Application software
1. General Purpose
2. Special Purpose

1. System Control Software:-
System software consists of programs that manage
system resources and functions.
It performs computer-related tasks, such as monitor,
control , coordinate and manage the resources.
The most important system control software is the
operating system.
Operating system:- An Operating system is a complex
set of software modules that manages the overall
operations of a computer.

2. System support software:-
That supports, or facilitates, the smooth and efficient
operation of a computer.
Example:-
Utility software- They perform tasks such as formatting
disks, locating free space on a disk, retrieving lost or
damaged files, sorting and merging data, converting files
from one form to another, backing up important files and
providing online help. Example : Antivirius
Language translators:- are support programs written
specifically to convert a program written in high-level
language into its equivalent machine language.

3. System Development Software:-
It consists of programs that assist system
developers in designing and build better
systems.
For example:- Computer-aided software
engineering (CASE) which is a collection of
programs that assist developers in developing an
information system.
Shells are also system development software,
shell is a set of tools and techniques that allows
developers to build a model of a system.

Application software is designed to perform people-
related tasks such as payroll, inventory and sales
analysis. These programs are generally user-friendly
permitting the user to specify his inputs in a manner
suitable to him and producing outputs in the form
desired by him. Application packages are written
using high-level language.
They are programs that are designed to meet the
specific computational needs of a group of users.
Application programs can be of 3 categories.
1. Open-ended software
2. Application-Specific software
3. User-specific Software

1. Open-ended software also called General-
purpose software .
These softwares perform general business
functions and are designed to perform wide
variety of tasks. They are designed to perform
functions with universal business application.
They include office suite applications such as word
processors, spreadsheets, simple databases,
graphic applications etc.
Microsoft Office is the most popular package used in
business. It contains the applications such as Word,
Excel, Access, Power-point..

2. Special Purpose Applications- These are the softwares
that are designed to perform or manage a specific
business function or process that is unique to a particular
industry. They include professional accounting software,
human resource management and customer relations
management software.
1. Application-Specific software:- Comprises of
programs dedicated to a specific function. They are
expensive and are developed to meet the needs of a large
organization. These include software's for accounting,
payroll, sales and inventory management etc..
2. User-specific Software:- refers to systems which are
commissioned to suit the needs of individual users.

Types of Computers:
The computer can be classified in different ways.
Classifications are:
1. Based on their construction and working
2. Based on application
3. Based on size speed and working.

1. Classification based on construction and working:
a. Analog computers:
•These computers are used to monitor continuously
changing signals, such as variation of temperature
and pressure in chemical plant. They contain analog
devices and handle information which is of physical
nature.
•Analog computers derive all their data from one form
of measurement. The accuracy of the data used in an
analog computer is directly related to the precision of
its measurements.
Eg: A petrol service station's pump contains an
analog processor that converts fuel flow
measurement into quantity and price.

b. Digital Computers
•A digital computer is designed to process data in
numerical form, its circuits perform directly the
mathematical operations of addition, subtraction,
multiplication, and division.
•The numbers operated on by a digital computer are
expressed in the binary system. A digital computer can
store the results of its calculations for later use, can
compare results with other data, and on the basis of such
comparisons can change the series of operations it
performs.
• Digital computers are used for reservations systems,
scientific Investigation, data-processing and word-
processing applications, desktop publishing, electronic
games, and many other purposes.

c. Hybrid Computer
•Hybrid computer is a digital computer that accepts
analog signals, converts them to digital and processes
them in digital form.
• This integration is obtained by digital to analog and
analog to digital converter.
•It accepts a continuously varying input, which is then
converted into a set of discrete values for digital
processing.
• An example of a hybrid computer is the computer
used in hospitals to measure the heartbeat of the
patient.

2. Classification based on applications:
a. General Purpose computers:
• These are designed to meet the needs of many
different applications.
• General purpose computers can store large
amounts of data and the programs necessary to
process them.
• These are versatile and mostly used in business
applications such as preparation of pay bill,
manage inventories, print sale reports.

b. Special purpose computers:
These computers are designed to cater the needs of
particular task or application.
-are designed to process only numeric data or to
completely control automated manufacturing processes.
-They do not possess unnecessary options and thus costs
less.
- examples are computers built into high end cameras.

1. Supercomputer:
• Fastest computers with extremely large storage
capacities and computing power. Can tackle tasks that
would not be practical for other computers.
2 characteristics are:
• a. parallel processing b. fault tolerant
Supercomputer has multiple processors that can process
multiple instructions at a time. In parallel processing, the
instructions are simultaneously executed by different
processors simultaneously.
For example: They are used in scientific research such as
weather forecast, weapon research, medicine etc.
3. Based on the size, speed and capability
computers are classified into:

2. Mainframe
 These are general purpose, large scale
expensive computer with huge storage
capacity capable of simultaneously
processing data for hundreds or
thousands of users.
 Used to store, manage, and process large
amounts of data that need to be reliable,
secure, and centralized.
 Usually housed in a closet sized cabinet.
 2 Types of terminals
 a. dumb b. intelligent
Dumb terminal does not have its own CPU
or storage device.
Intelligent terminal has a processor of its
own to provide some processing
capabilities.

3. Mini Computers
•Because of their smaller size they are called as
minis. Their capabilities lie between a mainframe
and a personal computers.
•They are mainly used in small business organizations.
•Mini computers are used as servers in network
environment wherein hundreds of personal
computers can be connected to a single
minicomputer in order to share data.

4. Workstation
 Desktop computer which is usually more powerful than a
Microcomputer.
 Powerful desktop computer designed for specialized
tasks.
 Can tackle tasks that require a lot of processing speed. It
will be used in banks.
 Can also be an ordinary personal computer attached to a
LAN (local area network).
 Used by designers, engineers, architects etc.

5. Microcomputer /Personal
computer
 A personal computer; designed to meet
the computer needs of an individual.
 Provides access to a wide variety of
computing applications, such as word
processing, photo editing, e-mail, and
internet.
 Microcomputer includes following type:
1. Laptops/Notebook Computer
2. Handheld Personal Computer

Laptop / Notebook Computer
 They are battery-
operated computers
that can be used
anywhere at any time.
 Main difference is their
size and weight.
 All components
(keyboard, mouse, etc.)
are in one compact unit.
 Usually more expensive
than a comparable
desktop.
 Sometimes called a
Notebook.

Handheld/palmtops
Handheld computers also called as palmtops.
They are smaller than notebook and can be easily
operated on palm.
1. PDA (Personal Digital Assistant).
Portable computers used for special applications.
A computer that fits into a pocket, runs on
batteries, and is used while holding in your hand.
 Typically used as an appointment book, address
book, calculator, and notepad.
3 categories: Personal Digital Assistant, Cellular phone, H/PC Pro
device

2. Cellular Phones:
Advanced cellular devices combine analog and
digital cell-phone services with e-mail
capabilities.
Such phones enable the user to check and
send e-mail and faxes over the phone.

3. H/PC Pro devices:
•These are larger than PDA's with features between
PDA's and notebooks.
•H/PC Pro devices are equipped with full-size
keyboards and color displays. They have longer
battery life and can run many smaller
applications.
•Disadvantage is that they have limited primary
memory and have slow processing speed.

The operating system (or OS) is a set of special programs that run on a
computer system that allow it to work properly.
They help it to load and save data; to communicate; and to run other
programs (applications software).
Because there are different types of computer, and different uses for them, there
are different types of operating system.

Functions of Operating System
Load programs:- Moves programs to be executed
into primary memory and indicate when program
execution is complete
Manage I/O:- Enables and manages the use of
multiple I/O devices. Ensures the operations efficient
utilization of I/O devices
Manage files:- Allows application programs to read
and write files. Performs other file- related operations
such as copying, deleting, moving and so on.

Manage Memory:- Allocates memory so users
can create, execute and retrieve different
applications. Ensures that memory is fully and
efficiently utilized.
Detect errors:- Brings system and execution
errors to the attention of the user so that timely
action can be taken.
Allocate resources:- Manages all computer
resources, including the CPU, primary memory,
secondary storage, and I/O devices and other
peripherals.

Storage Devices
A storage device is used in the computers to store the
data.
1. Primary Storage
• Also known as main memory.
• Main memory is directly or indirectly connected to
the central processing unit via a memory bus.
• The CPU continuously reads instructions stored there
and executes them as required.
• Example: – RAM – ROM – Cache

Primary Storage
RAM
• It is called Random Access Memory because any of the data in RAM can be
accessed just as fast as any of the other data.
• There are two types of RAM:
– DRAM (Dynamic Random Access Memory)
– SRAM (Static Random Access Memory)

Primary Storage
ROM
• This memory is used as the computer begins to boot up.
• Small programs called firmware are often stored in ROM
chips on hardware devices (like a BIOS chip), and they
contain instructions the computer can use in performing
some of the most basic operations required to operate
hardware devices.
• ROM memory cannot be easily or quickly overwritten or
modified

Primary Storage
Cache
• Cache is a high-speed access area that can be
either a reserved section of main memory or a
storage device.
• Most computers today come with L3 cache or
L2 cache, while older computers included only
L1 cache

Secondary Storage
• It is not directly accessible by the CPU.
• Computer usually uses its input/output channels to
access secondary storage and transfers the desired data
using intermediate area in primary storage.
• Example: – Hard disk

Floppy Disk
• A soft magnetic disk.
• Floppy disks are portable.
• Floppy disks are slower to access than hard
disks and have less storage capacity, but they are
much less expensive.
• Can store data up to 1.44MB.
• Two common sizes: 5 ¼” and 3 ½”.

Optical Disc
• Optical disc is any storage media that holds content in
digital format and is read using a laser assembly is
considered optical media.
• The most common types of optical media are
– Compact Disc (CD)
– Digital Versatile Disc (DVD)

USB Flash Drive
• A small, portable flash memory card that plugs
into a computer’s USB port and functions as a
portable hard drive.
• Flash drives are available in sizes such as 256MB,
512MB, 1GB, 5GB, and 16GB and are an easy way to
transfer and store information.

Volatility
• Two types of volatility:
– Volatile Memory
– Non-Volatile Memory

Volatile Memory
Requires constant power to maintain the
stored information.
• The fastest memory technologies.
• All contents are erased when the system's
power is turned off or interrupted.
• It has been more popularly known as
temporary memory.

Non-Volatile Memory
• Will retain the stored information even if it is
not constantly supplied with electric power.
• Non volatile memory is the device which keeps
the data even when the current is off.
• It is suitable for long-term storage of
information.

Input Device : A piece of equipment/hardware
which helps us enter data into a computer is
called an input device. For example keyboard,
mouse, etc.
Output Device : A piece of
equipment/hardware which gives out the result
of the entered input, once it is processed (i.e.
converts data from machine language to a
human-understandable language), is called an
output device. For example printer, monitor, etc.

List of Input Devices
Keyboard
A simple device comprising keys and each key denotes
either an alphabet, number or number commands which
can be given to a computer for various actions to be
performed
It has a modified version of typewriter keys
The keyboard is an essential input device and computer and
laptops both use keyboards to give commands to the
computer

Mouse
It is also known as a pointing device
Using mouse we can directly click on the various icons
present on the system and open up various files and
programs
A mouse comprises 3 buttons on the top and one
trackball at the bottom which helps in selecting and
moving the mouse around, respectively
In case of laptops, the touchpad is given as a
replacement of the mouse which helps in the
movement of the mouse pointer

Joy Stick
It is a device which comprises a stick which is attached at an
angle to the base so that it can be moved and controlled
Mostly used to control the movement in video games
Apart from a computer system, a joystick is also used in the
cockpit of an aeroplane, wheelchairs, cranes, trucks, etc. to
operate them well
Light Pen
It is a wand-like looking device which can directly be moved
over the device’s screen
It is light-sensitive
Used in conjunction with computer’s cathode ray tube

Microphone
Using a microphone, sound can be stored in a device in its
digital form. It converts sound into an electrical signal. To
record or reproduce a sound created using a microphone, it
needs to be connected with an amplifier
Scanner
This device can scan images or text and convert it into a
digital signal. When we place any piece of a document on a
scanner, it converts it into a digital signal and displays it on
the computer screen
Barcode Reader
It is a kind of an optical scanner. It can read bar codes
A source of light is passed through a bar code, and its
aspects and details are displayed on the screen

Output Devices
The commonly used output devices have been listed below with a brief summary of
what their function is and how they can be used.
Monitor
The device which displays all the icons, text, images, etc. over a screen is called
the Monitor
When we ask the computer to perform an action, the result of that action is
displayed on the monitor
Various types of monitors have also been developed over the years
Printer
A device which makes a copy of the pictorial or textual content, usually over a
paper is called a printer
For example, an author types the entire book on his/her computer and later
gets a print out of it, which is in the form of paper and is later published
Multiple types of printers are also available in the market, which can serve
different purposes

Speakers
A device through which we can listen to a sound as an
outcome of what we command a computer to do is
called a speaker
Speakers are attached with a computer system and
also are a hardware device which can be attached
separately
With the advancement in technology, speakers are
now available which are wireless and can be
connected using BlueTooth or other applications

Projector
An optical device which presents an image or
moving images onto a projection screen is
called a projector
Most commonly these projectors are used in
auditoriums and movie theatres for the
display of the videos or lighting
If a projector is connected to a computer,
then the image/video displayed on the
screen is the same as the one displayed on
the computer screen

Headphones
They perform the same function as a speaker, the
only difference is the frequency of sound
Using speakers, the sound can be heard over a larger
area and using headphones, the sound is only
audible to the person using them
Also known as earphones or headset

Output Devices
 Printers
 Impact printers
Dot matrix printers
 Nonimpact printers
Ink jet
Laser
Color
B & W
 Monitors
 CRT’S
 LCD’S

Monitors or Visual Display Unit(VDU) are television like
devices for displaying the output of computers.

A printer is an output device that produces text and
graphics on a physical medium such as paper. Since the
printed information exists permanently on a physical
media they are called hard copy.
1. An impact printer forms characters and graphics on
a piece of paper by striking an inked ribbon against
the paper with a hammer like mechanism.
Eg: Dot matrix printer, Line printer
2. Nonimpact printer: Eg: Inkjet printer, Laser
printer

STORAGE DEVICES
 Floppy Disks
 3.5-inch disks store 1.44M of data
 Must be formatted
 Tracks
 sectors
 Hard Disks
 Spins at 5,400 – 7,200 rpm (revolutions per minute)
 Can store anywhere between 10G – 250G+ of data
 CD’s—Compact Discs
 Available in a variety of formats—CD-ROM, CD-R, CD-RW
 A typical CD holds about 650 MB of data
 DVD’s
 Available as DVD-ROM, DVD-R, DVD-RW
 Can hold 4.7 GB of data
 Zip Drives—high capacity floppy disk drive; has lost popularity
 Zip disks can hold from 100 MB – 250 MB of data
 USB Flash Drive
 Storage capacity between 32 MB – 4 GB

Data Representation
Bit is either 0 or 1
Byte—8 bits i.e. one character of data
Kilobyte—thousand twenty four bytes of data
Megabyte—thousand twenty four kilobytes
Gigabyte—thousand twenty four megabytes
Terabyte—thousand twenty four gigabytes

Introduction to computers MRS. SOWMYA JYOTHI

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Introduction to computers MRS. SOWMYA JYOTHI