Introduction to computer

Introduction to
computer
Techmology
BY LECTURER.SURAJ PANDEY CCT COLLEGE

Definition of computer
• The term computer is derived from the word compute.
The word compute means to calculate. A computer is an
electronic machine that accepts data from the user,
processes the data by performing calculations and
operations on it, and generates the desired output results.
Computer performs both simple and complex operations,
with speed and accuracy.

• Functionalities of a computer
Any digital computer carries out five functions in gross
terms:
1.Takes data as input.
2.Stores the data/instructions in its memory and use them
when required.
3.Processes the data and converts it into useful information.
4.Generates the output
5.Controls all the above four steps.

Advantages of computer
1. High Speed
Computer is a very fast device.
 It is capable of performing calculation of very large
amount of data.
 The computer has units of speed in microsecond,
nanosecond, and even the picosecond.
It can perform millions of calculations in a few seconds
as compared to man who will spend many months for
doing the same task.

2. Accuracy
 In addition to being very fast, computers are very
accurate.
The calculations are 100% error free.
Computers perform all jobs with 100% accuracy
provided that correct input has been given.

3.Storage Capability
Memory is a very important characteristic of computers.
A computer has much more storage capacity than human
beings.
It can store large amount of data.
It can store any type of data such as images, videos, text,
audio and many others.

4. Diligence
Unlike human beings, a computer is free from monotony,
tiredness and lack of concentration.
It can work continuously without any error and boredom.
It can do repeated work with same speed and accuracy.

5. Versatility
A computer is a very versatile machine.
A computer is very flexible in performing the jobs to be
done.
 At one moment you can use the computer to prepare a
letter document and in the next moment you may play
music or print a document.

6. Reliability
A computer is a reliable machine.
Modern electronic components have long lives.
Computers are designed to make maintenance easy.

7. Automation
Computer is an automatic machine.
Automation means ability to perform the given task
automatically.
Once a program is given to computer i.e. stored in
computer memory, the program and instruction can
control the program execution without human interaction.

8. Reduction in Paper Work
 The use of computers for data processing in an
organization leads to reduction in paper work and results
in speeding up a process.
As data in electronic files can be retrieved as and when
required, the problem of maintenance of large number of
paper files gets reduced.

9. Reduction in Cost
Though the initial investment for installing a computer is
high but it substantially reduces the cost of each of its
transaction.

Disadvantages
Following list demonstrates the disadvantages of
computers in today's arena.
1. NoI.Q
 A computer is a machine that has no intelligence to
perform any task.
 Each instruction has to be given to computer.
A computer cannot take any decision on its own.

2. Dependency
It functions as per a user’s instruction, so it is fully
dependent on human being.
3. Environment
 The operating environment of computer should be dust
free and suitable.
4. No Feeling
Computers have no feelings or emotions.
It cannot make judgment based on feeling, taste,
experience, and knowledge unlike a human being.

5. Unemployment
• Different tasks are performed automatically by using
computers. It reduces the need of people and increases
unemployment in society.

7. Data Security
• The data stored on a computer can be accessed by
unauthorized persons through networks. It has created serious
problems for the data security.
8. Computer Crimes
• People use the computer for negative activities. They hack the
credit card numbers of the people and misuse them or they can
steal important data from big organizations.
9. Privacy violation
• The computers are used to store personal data of the people.
The privacy of a person can be violated if the personal and
confidential records are not protected properly.

Application area
Business
 A computer has high speed of calculation,
diligence, accuracy, reliability, or versatility
which made it an integrated part in all business
organisations.
 Computer is used in business organisations for:
 Payroll calculations
 Budgeting
 Sales analysis
 Financial forecasting
 Managing employees database
 Maintenance of stocks etc.

2. Banking
Today banking is almost totally dependent on
computer.
Banks provide following facilities:
Banks provide online accounting facility, which
includes current balances, deposits, overdrafts,
interest charges, shares, and trustee records.
ATM machines are making it even easier for
customers to deal with banks.

Insurance
Insurance companies are keeping all records up-to-
date with the help of computers. The insurance
companies, finance houses and stock broking firms
are widely using computers for their concerns.
Insurance companies are maintaining a database of
all clients with information showing
•procedure to continue with policies
•starting date of the policies
•next due installment of a policy
•maturity date
•interests due
•survival benefits
•bonus

3. Education
The computer has provided a lot of
facilities in the education system.
The computer provides a tool in the
education system known as CBE
(Computer Based Education). CBE
involves control, delivery, and evaluation
of learning.
The computer education is rapidly
increasing the graph of number of
computer students.
There are number of methods in which
educational institutions can use computer
to educate the students.
 It is used to prepare a database about
performance of a student and analysis is
carried out on this basis.

4. Marketing
In marketing, uses of computer are following:
Advertising - With computers, advertising
professionals create art and graphics, write and revise
copy, and print and disseminate ads with the goal of
selling more products.
At Home Shopping - Home shopping has been
made possible through use of computerised catalogues
that provide access to product information and permit
direct entry of orders to be filled by the customers.

5. Health Care
Computers have become important part in
hospitals, labs, and dispensaries. The
computers are being used in hospitals to keep
the record of patients and medicines. It is also
used in scanning and diagnosing different
diseases. ECG, EEG, Ultrasounds and CT
Scans etc. are also done by computerised
machines.

6.Engineering Design
Computers are widely used in Engineering purpose.
One of major areas is CAD (Computer aided design).that provides creation and modification of
images.

7. Military
Computers are largely used in defence. modern tanks,
missiles, weapons etc. Military also employs
computerised control systems. Some military areas
where a computer has been used are:
 Missile Control
Military Communication
Military Operation and Planning
Smart Weapons

Communication
Communication means to convey a
message, an idea, a picture or speech that
is received and understood clearly and
correctly by the person for whom it is
meant for. Some main areas in this
category are:
E-mail
Chatting
Usenet
FTP
Telnet
Video-conferencing

Types of computer
• The computer is divided into three broad category has its
own categories given below:

ComputerComputer
Digital ComputerDigital Computer Analog ComputerAnalog Computer Hybrid ComputerHybrid Computer
Size and
Performance
Size and
Performance
PurposePurpose
Super
Computer
Super
Computer
SpecialSpecial GeneralGeneral
Mainframe
Computer
Mainframe
Computer
Mini
Computer
Mini
Computer
Micro
Computer
Micro
Computer

On the basis of work
Digital computer Analog Computer Hybrid Computer
Computer that use binary
digits to display discrete
information is called
digital computer
A computer that uses
analog signal to display
information is called
analog computer
A computer that is able
to understand binary as
well as analog signal to
display information is
called hybrid computer
Information is in discrete
form. It displays
information in the form
of text, graphics and
pictures
Information in
continuous form and
displayed in the form of
curves. It is used to
measure continuous
physical quantity like as
current flow,
temperatures, blood
pressure, heart beats.
Information depends on
operating mode of
computers. It can display
information in discrete
and continuous form
because its one part is
dedicated for digital
processing and next part
is for analog processing
Slow Fast Intermediate in speed

On the basis of size:
• According to size
• Supercomputers
• Mainframe Computers
• Minicomputers
• Workstations
• Microcomputers, or Personal Computers

• Supercomputers :
are widely used in scientific applications such as aerodynamic
design simulation, processing of geological data.
• Supercomputers are the most powerful computers. They are
used for problems requiring complex calculations.
• Because of their size and expense, supercomputers are
relatively rare.
• Supercomputers are used by universities, government
agencies, and large businesses.
• For example, weather forecasting requires a supercomputer.

• Mainframe Computers:
are usually slower, less powerful and less expensive than
supercomputers. A technique that allows many people at
terminals, to access the same computer at one time is called
time sharing. Mainframes are used by banks and many business
to update inventory etc.
• Mainframe computers can support hundreds or thousands of
users, handling massive amounts of input, output, and storage.
• Mainframe computers are used in large organizations where
many users need access to shared data and programs.
• Mainframes are also used as e-commerce servers, handling
transactions over the Internet.

• Minicomputers:
are smaller than mainframe, general purpose computers,
and give computing power without adding the prohibitive
expenses associated with larger systems. It is generally
easier to use.
• Minicomputers usually have multiple terminals.
• Minicomputers may be used as network servers and
Internet servers, credit card processing, Air traffic control
system.

• Microcomputers, or Personal Computers :
is the smallest, least expensive of all the computers. Micro
computers have smallest memory and less power, are
physically smaller and permit fewer peripherals to be attached.
• Microcomputers are more commonly known as personal
computers. The term “PC” is applied to IBM-PCs or
compatible computers.
• Desktop computers are the most common type of PC.
• Notebook (laptop) computers are used by people who need
the power of a desktop system, but also portability.
• Handheld PCs (such as PDAs) lack the power of a desktop or
notebook PC, but offer features for users who need limited
functions and small size.

• Personal Computers(PC):
Desk Top
• Lap Top
• Palm Top
• PDA

According to Purpose
•
1. General purpose Computers
2. Special Computers
• General purpose Computers
A ‘General Purpose Computer’ is a machine that is capable of
carrying out some general data processing under program control.
Refers to computers that follow instructions, thus virtually all
computers from micro to mainframe are general purpose. Even
computers in toys, games and single-function devices follow
instructions in their built-in program.

• Special purpose Computers
A computer that is designed to operate on a restricted
class of problems.
Use special purpose computer equipment to obtain
patient diagnostic information.

Computer
System/components of
Computer system
• Computer system consist of :
• Input
• Output
• Processor
• Storage: a) Primary storage b) Secondary Storage

• Input
• Input devices enable us to get information into a
computer. Some examples include a keyboard, mouse,
microphone, scanner, or digital camera.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

 Storage
There are two types of storage: primary/temporary and
secondary/long-term. RAM, or random access memory,
is temporary, meaning it stores information as you use
it, but it is being constantly erased and rewritten as you
open and close files.
Long-term storage holds information for as long as you
want it. Hard drives, portable hard drives, floppy drives,
flash drives, CD’s, and DVD’s are long term storage
devices.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

• Processor
• A microprocessor controls the computers’ functions. It
is smaller than a dime, but contains millions of
transistors that perform millions of instructions per
second. The microprocessor performs these instructions
using a three-step process: fetch, decode and execute.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

• Output
• Information that has been processed is communicated
back to the user in the form of words, sounds or pictures,
and is delivered through printers, speakers, monitors or
other output devices. Sometimes output is just written
back to a storage device.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

Block diagram of
Computer

Auxiliary Memory
Main Memory
ALU
Control Unit
Input Unit Output Unit
Block Diagram

• The working mechanism of computer is not simple, it is
a complex machine so, and its working mechanism is
also very complex . Here ,only the summary of working
mechanism is presented in simple words:
a)Main memory,ALU and control unit is main part of
CPU. All input data is stored in main memory. The
keyboard is a standard input device. When we input data
through it, data is stored in buffer storage of keyboard,
until enter key is pressed.
b)Data come to ALU for processing, data is returned back
to main memory. Main memory
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

is used as dark room of theatre where actors/actress are
masking themselves before going to stage and return
back again after finishing their performance.
c) From main memory, data go to secondary memory
(Floppy, Hard Disk etc) for permanent storage or may
directed to go printer for hard copy
d) We take data or any information from secondary
memory. These data may be processed in ALU then
either return to secondary memory or go to output unit.
e) The control unit controls ALU, main memory,
input/output unit, secondary memory and other
peripherals.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

Computer - CPU
• CPU is considered as the brain of the computer.
• CPU performs all types of data processing operations.
• It stores data, intermediate result and instructions (program).
• It controls the operations of all parts of computer.
• CPU itself has the following three components.
• Memory or Storage Unit:
• Control Unit
• ALU (Arithmetic Logic Unit)

BY LECTURER.SURAJ
PANDEY CCT COLLEGE

• Input Unit:-
• Computers accept coded information through input units,
which read the data. The most well-known input device
is keyboard. Whenever a key is pressed, the
corresponding letter or digit is automatically translated
into its corresponding binary code and transmitted over a
cable to either the memory or the processor
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

• Output Unit:-
• Its function is to send processed result to the outside
world. Ex:- Printer.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

Memory Or Storage
Unit:
• This unit can store instructions, data and intermediate results.
This unit supplies information to the other units of the
computer when needed. It is also known as internal storage
unit or main memory or primary storage or Random access
memory(RAM).
• Its size affects speed, power and capability. There are primary
memory and secondary memory, two types of memories in the
computer. Functions of Memory Unit are:
• It stores all the data to be processed and the

instructions required for processing.
• It stores intermediate results of processing.
• It stores final results of processing before these results
are released to an output device.
• All inputs and outputs are transmitted through main
memory.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

Control Unit
• This unit controls the operations of all parts of computer.
It does not carry out any actual data processing
operations.
• Functions of this unit are:
• It is responsible for controlling the transfer of data and
instructions among other units of a computer.
• It manages and coordinates all the units of the computer.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

• It obtains the instructions from the memory, interprets
them and directs the operation of the computer.
• It communicates with Input/Output devices for transfer
of data or results from storage.
• It does not process or store data.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

ALU (Arithmetic Logic
Unit)
• This unit consists of two subsections namely:
• Arithmetic Section
• Logic Section
• Arithmetic Section
• Function of Arithmetic section is to perform arithmetic
operations like addition, subtraction, multiplication and
division. All complex operations are done by making
repetitive use of above operations.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

• Logic Section
• Function of logic section is to perform logic operations
such as comparing, selecting, matching and merging of
data.
BY LECTURER.SURAJ
PANDEY CCT COLLEGE

Computer
Memory

Computer-Memory
• A memory is just like a human brain. It is used to store
data and instructions. Computer memory is the storage
space in computer where data is to be processed and
instructions required for processing are stored.
• The memory is divided into large number of small parts.
Each part is called cell.

• Memory is primarily of three types:
1.Cache Memory
2.Primary Memory/Main Memory
3.Secondary Memory

Cache Memory
Cache memory is a very high speed semiconductor
memory, which can speed up CPU. It acts as a buffer
between the CPU and main memory.
It is used to hold those parts of data and program which
are most frequently used by CPU. The parts of data and
programs are transferred from disk to cache memory by
operating system, from where CPU can access them. The
advantage of cache memory is that the CPU does not
have to use the motherboard’s system bus for data
transfer.

• Advantage
1.Cache memory is faster than main memory.
2.It consumes less access time as compared to main memory.
3.It stores the program that can be executed within a short
period of time.
4.It stores data for temporary use.
5.Disadvantage:
6.Cache memory has limited capacity.
7.It is very expensive.

Function of cache
memory

Primary Memory (Main Memory)
• Primary memory holds only those data and instructions
on which computer is currently working. It has limited
capacity and data gets lost when power is switched off.
• It is generally made up of semiconductor device. It is
divided into two subcategories RAM and ROM.

• Characteristic of Main Memory
1.These are semiconductor memories.
2.It is known as main memory.
3.Usually volatile memory.
4.Data is lost in case power is switched off.
5.It is working memory of the computer.
6.Faster than secondary memories.
7.A computer cannot run without primary memory.

Computer - RAM
• A RAM constitutes the internal memory of the CPU for
storing data, program and program result. It is read/write
memory. It is called random access memory (RAM).
• Since access time in RAM is independent of the address
to the word that is, each storage location inside the
memory is as easy to reach as other location & takes the
same amount of time. We can reach into the memory at
random & extremely fast but can also be quite
expensive.

• RAM is volatile, i.e., data stored in it is lost when we
switch off the computer or if there is a power failure.
Hence, a backup uninterruptible power system (UPS) is
often used with computers. RAM is small, both in terms
of its physical size and in the amount of data it can hold.
• RAM is of two types:
• Static RAM (SRAM)
• Dynamic RAM (DRAM)

Static RAM (SRAM)
• The word static indicates that the memory retains its contents
as long as power remains applied. However, data is lost when
the power gets down due to volatile nature. Transistors do not
require power to prevent leakage, so SRAM need not have to
be refreshed on a regular basis.
• Because of the extra space in the matrix, SRAM uses more
chips than DRAM for the same amount of storage space, thus
making the manufacturing costs higher.

• Static RAM is used as cache memory needs to be very fast and
small.
• Characteristics of the Static RAM:
• It has long data lifetime
• There is no need to refresh
• Faster
• Used as cache memory
• Large size
• Expensive
• High power consumption

• Dynamic RAM (DRAM)
• DRAM, unlike SRAM, must be continually refreshed in
order for it to maintain the data. This is done by placing
the memory on a refresh circuit that rewrites the data
several hundred times per second. DRAM is used for
most system memory because it is cheap and small. All
DRAMs are made up of memory cells. These cells are
composed of one capacitor and one transistor.

• Characteristics of the Dynamic RAM:
• It has short data lifetime
• Need to refresh continuously
• Slower as compared to SRAM
• Used as RAM
• Lesser in size
• Less expensive
• Less power consumption

Computer - ROM
• ROM stands for Read Only Memory. The memory from which
we can only read but cannot write on it. This type of memory
is non-volatile. The information is stored permanently in such
memories during manufacture.
• A ROM stores such instructions as are required to start
computer when electricity is first turned on, this operation is
referred to as bootstrap. ROM chip are not only used in the
computer but also in other electronic items like washing
machine and microwave oven.

• Following are the various types of ROM:
• MROM (Masked ROM)
• The very first ROMs were hard-wired devices that
contained a pre-programmed set of data or instructions.
These kinds of ROMs are known as masked ROMs. It is
inexpensive ROM.
• PROM (Programmable Read only Memory)

• PROM is read-only memory that can be modified only
once by a user. The user buys a blank PROM and enters
the desired contents using a PROM programmer. Inside
the PROM chip, there are small fuses, which are burnt
open during programming. It can be programmed only
once and is not erasable.

EPROM (Erasable and Programmable
Read Only Memory)
The EPROM can be erased by exposing it to ultra-violet
light for a duration of up to 40 minutes. Usually, an EPROM
eraser achieves this function. During programming, an
electrical charge is trapped in an insulated gate region. The
charge is retained for more than ten years because the charge
has no leakage path. For erasing this charge, ultra-violet light
is passed through a quartz crystal window (lid).

EEPROM (Electrically Erasable and
Programmable Read Only Memory)
• The EEPROM is programmed and erased electrically. It
can be erased and reprogrammed about ten thousand
times. Both erasing and programming take about 4 to 10
ms (milli second). In EEPROM, any location can be
selectively erased and programmed. EEPROMs can be
erased one byte at a time, rather than erasing the entire
chip. Hence, the process of re-programming is flexible
but slow.

• Advantages of ROM
• Non-volatile in nature
• These can not be accidentally changed
• Cheaper than RAMs
• Easy to test
• More Reliable than RAMs
• These are static and do not require refreshing
• Its contents are always known and can be verified

Secondary Memory
• This type of memory is also known as external memory
or non-volatile. It is slower than main memory. These
are used for storing Data/Information permanently.

Characteristics of Secondary Memory
1.These are magnetic and optical memories.
2.It is known as backup memory.
3.It is non-volatile memory.
4.Data is permanently stored even if power is switched off.
5.It is used for storage of the data in the computer.
6.Computer may run without secondary memory.
7.Slower than primary memories.

Introduction to computer

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Introduction to computer