Functionalities of a computer, and Generations of Computer

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

Definition
Computer is an electronic data processing device which
• accepts and stores data input,
• processes the data input, and
• generates the output in a required format.

Advantages
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.

 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.

 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.

 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.

 Versatility
• A computer is a very versatile machine.
• A computer is very flexible in performing the jobs to be done.
• This machine can be used to solve the problems related to various
fields.
• At one instance, it may be solving a complex scientific problem and
the very next moment it may be playing a card game.

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

 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.
 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
 No I.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.
 Dependency
• It functions as per a user’s instruction, so it is fully dependent on human
being

 Environment
• The operating environment of computer should be dust free
and suitable.
 No Feeling
• Computers have no feelings or emotions.
• It cannot make judgement based on feeling, taste, experience,
and knowledge unlike a human being.

Applications
 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.

 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

 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.

 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.

 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.
Some major fields of health care in which computers are used are :
• Diagnostic System - Computers are used to collect data and identify cause of
illness.
• Lab-diagnostic System - All tests can be done and reports are prepared by
computer.
• Patient Monitoring System - These are used to check patient's signs for
abnormality such as in Cardiac Arrest, ECG etc.
• Pharma Information System - Computer checks Drug-Labels, Expiry dates,
harmful drug’s side effects etc.
• Surgery : Nowadays, computers are also used in performing surgery.

 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. Some fields are:
• Structural Engineering - Requires stress and strain analysis for design of
Ships, Buildings, Budgets, Airplanes etc.
• Industrial Engineering - Computers deal with design, implementation and
improvement of integrated systems of people, materials and equipments.
• Architectural Engineering - Computers help in planning towns, designing
buildings, determining a range of buildings on a site using both 2D and 3D
drawings.

 Military
• Computers are largely used in defense. Modern tanks, missiles,
weapons etc. Military also employs computerized 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

 Government
• Computers play an important role in government. Some major
fields in this category are:
• Budgets
• Sales tax department
• Income tax department
• Male/Female ratio
• Computerization of voters lists
• Computerization of driving licensing system
• Computerization of PAN card
• Weather forecasting

Generations of Computer –
On basis of size and speed

First Generation Computers – 1942- 1955
• Bulky in size
• Highly unreliable
• Limited commercial use commercial production difficult and
costly
• Difficult to use
• Based on Vacuum tubes
• Machine and assembly languages
• Used for mostly scientific applications
• Examples – ENIAC, EDVAC, IBM 701

Second Generation Computers – 1955- 1964
• Faster, smaller
• More reliable
• Commercial production was still difficult and costly
• Easier to program than previous generation computers
• Based on transistors
• High level programming languages
• Used for scientific and commercial applications
• Examples – Honeywell 400, IBM 7030, CDC 1604

Third Generation Computer – 1964- 1975
• Faster, smaller
• More reliable
• Easier and cheaper to produce commercially
• Easier to use and easier to upgrade than previous generation systems
• Scientific , commercial and online applications
• Based on ICs with SSI and MSI technologies
• Timesharing Operating system
• Standardization of high level programming languages
• Examples – IBM 360/370, PDP -8, PDP-11, CDC 6600

Fourth Generation Computers – 1975-1989
• Small, affordable, reliable and easy to use PCs, more powerful and reliable
mainframe systems
• General purpose machines
• Easier to use commercially
• Based on ICs with VLSI technology
• UNIX Operating systems , GUI multiple windows on a single terminal
screen
• C, C++ programming languages
• Object oriented software design
• Hard disk – secondary storage, Floppy disks and magnetic tapes as
portable storage media
• Example – IBM PC, APPLE II, CRAY -1,CRAY-2,CRAY-X/MP

Fifth Generation Computers – 1989 – Present
• Portable Computers
• More powerful, cheaper, reliable, easier to use desktop machines
• Very powerful mainframes, general purpose machines, easier to produce
commercially
• Based on ICs with ULSI technology
• Larger capacity hard disk,
• Notebook computers, powerful desktop PCs and workstations
Supercomputers based on parallel processing, the internet(world wide
web)
• Multimedia and internet based applications
• JAVA programming languages
• Examples – IBM notebooks, Pentium PCs, SUN workstations, PARAM
supercomputers

ON THE BASIS OF FUNCTIONALITY:
According to functionality computer can be divided in to three types:
1. Analog
2. Digital
3. Hybrid

ANALOG COMPUTERS:
DEFINITION:
· “An analog (spelled analogue in British English) computer is a
form of computer that uses the continuously-changeable aspects
of physical fact such as electrical, mechanical, or hydraulic
quantities to model the problem being solved.”
· Analog means continuity of associated quantity just like
an analog clock measures time by means of the distance traveled
by the hand of the clock around a dial.

EXAMPLES:
· Thermometer
· Analog clock
· Speedometer
· Tire pressure gauge
ADVANTAGES:
· Analog computer has come to refer to
. devices and media that represent
. Store images
. Sound, motion pictures, etc.
DISADVANTAGES:
· Analog computers can have a very wide range of complexity.
· Very complicated for containing output for the users some time.

DIGITAL COMPUTERS:
DEFINITION:
· “A computer that performs calculations and logical
operations with quantities represented as digits, usually in the
binary number system of “0” and “1”.
· “Computer capable of solving problems by processing
information expressed in discrete form. By manipulating
combinations of binary digits (“0”, “1”), it can perform
mathematical calculations, organize and analyze data, control
industrial and other processes, and simulate dynamic systems
such as global weather patterns. ”
EXAMPLES:
· IBM PC
· Apple Macintosh
· Calculators
· Digital watches etc

HYBRID COMPUTERS:
DEFINITION:
· “A computer that processes both analog and digital data”.
· “Hybrid computer is a digital computer that accepts analog
signals, converts them to digital and processes them in digital form”
A hybrid computer may use or produce analog data or digital data. It
accepts a continuously varying input, which is then converted into a
set of discrete values for digital processing.
Examples:
· Hybrid computer is the computer used in hospitals to measure
the heartbeat of the patient.
· Devices used in petrol pump.
· Hybrid Machines are generally used in scientific applications or
in controlling industrial processes.

 Small
 relatively inexpensive computer with a microprocessor as
its central processing unit (CPU)
 includes a microprocessor, memory, and minimal
input/output (I/O) circuitry mounted on a single
printed circuit board
 Microcomputers became popular in the 1970s and 1980s
with the advent of increasingly powerful microprocessors
Micro Computer

 developed in the 1960s
 to describe the smaller computers that became
possible with the use of transistors and
core memory technologies
 the term "minicomputer" came to mean a
machine that lies in the middle range of the
computing spectrum, in between the smallest
mainframe computers and the microcomputers.
Mini Computer

 are computers used primarily by large organizations for critical
applications,
 bulk data processing,
 such as census,
 industry and consumer statistics,
 enterprise resource planning,
 and transaction processing.
Mainframes

 A supercomputer is a computer with a high level of
computing performance compared to a
general-purpose computer.
 Performance of a supercomputer is measured in
floating-point operations per second (FLOPS) instead of
million instructions per second (MIPS).
 The majority of supercomputers today run Linux-based
operating systems.
Super Computer

 Computers need to receive data and instruction in order to solve any
problem.
 Therefore we need to input the data and instructions into the computers.
 The input unit consists of one or more input devices.
 Keyboard is the one of the most commonly used input device.
 Other commonly used input devices are the mouse, floppy disk drive,
magnetic tape, etc.
 All the input devices perform the following functions.
• Accept the data and instructions from the outside world.
• Convert it to a form that the computer can understand.
• Supply the converted data to the computer system for further processing.

Storage Unit:
• The storage unit of the computer holds data and instructions that
are entered through the input unit, before they are processed.
• It preserves the intermediate and final results before these are sent
to the output devices.
• It also saves the data for the later use.

 Primary Storage:
• Stores and provides data very fast.
• This memory is generally used to hold the program being currently
executed in the computer, the data being received from the input unit,
the intermediate and final results of the program.
• The primary memory is temporary in nature.
• The data is lost, when the computer is switched off.
• In order to store the data permanently, the data has to be transferred
to the secondary memory. Very small portion of primary storage
memory is permanent is nature eg. ROM which holds the data
permanent even if power off.
• The cost of the primary storage is more or compared to the
secondary storage. Therefore most computers have limited primary
storage capacity.

Secondary Storage:
• Secondary storage is used like an archive.
• It stores several programs, documents, data bases etc.
• The programs that you run on the computer are first
transferred to the primary memory before it is actually run.
• Whenever the results are saved, again they get stored in the
secondary memory.
• The secondary memory is slower and cheaper than the
primary memory.
• Some of the commonly used secondary memory devices are
Hard disk, CD, etc.,

Memory Size:
• All digital computers use the binary system, i.e. 0’s and 1’s.
• Each character or a number is represented by an 8 bit code.
• The set of 8 bits is called a byte.
• A character occupies 1 byte space.
• A numeric occupies 2 byte space.
• Byte is the space occupied in the memory.
• The size of the primary storage is specified in KB (Kilobytes) or MB
(Megabyte).
• One KB is equal to 1024 bytes and one MB is equal to 1000KB.
• The size of the primary storage in a typical PC usually starts at 160 GB. PCs
having 320 GB, 500 GB,1 TB memory are quite common.

Output Unit:
• The output unit of a computer provides the information and results
of a computation to outside world.
• Printers, Visual Display Unit (VDU) are the commonly used output
devices.
• Other commonly used output devices are floppy disk drive, hard disk
drive, and magnetic tape drive.

Central Processing Unit:
The control unit and ALU of the computer are together known as the
Central Processing Unit (CPU).
The CPU is like brain performs the following functions:
• It performs all calculations.
• It takes all decisions.
• It controls all units of the computer.
A PC may have CPU-IC such as Intel 8088, 80286, 80386, 80486, Celeron,
Pentium, Pentium Pro, Pentium II, Pentium III, Pentium IV, Dual Core,
AMD, i3, i5,i7 etc.

Arithmetic Logical Unit:
• All calculations are performed in the Arithmetic Logic Unit (ALU) of the
computer.
• It also does comparison and takes decision.
• The ALU can perform basic operations such as addition, subtraction,
multiplication, division, etc. and does logic operations viz, >, <, =, ‘etc.
• Whenever calculations are required, the control unit transfers the data
from storage unit to ALU once the computations are done, the results are
transferred to the storage unit by the control unit and then it is send to
the output unit for displaying results.

Control Unit:
• It controls all other units in the computer.
• The control unit instructs the input unit, where to store the data
after receiving it from the user.
• It controls the flow of data and instructions from the storage unit
to ALU.
• It also controls the flow of results from the ALU to the storage
unit.
• The control unit is generally referred as the central nervous
system of the computer that control and synchronizes it’s
working.

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