introduction to information technology (2015 16) unit 1

Introduction to Information Technology

S.N.Selvaraj, M.B.A., M.Phil., Assistant Professor, Email: [email protected]

Semester II

UNIT – I INTRODUCTION TO INFORMATION TECHNOLOGY

Types of computer systems – Micro, Mini, Main frame and super computers –

Analogue, digital and hybrid computers – Business and scientific computer systems –

First, second, third and fourth generation computers – Laptop or Note book

computers – Data processing systems – Batch-Online and real time systems – Time

sharing – Multi programming and Multi processing systems – Net-working – Local

Area and Wide Area Net-works.

Introduction of a Computer

The origin of computer technology took place in the 19th century. People desired to

have a machine that would carry out mathematical calculations for them. The

ABACUS is considered to have been the first computer in the world. It was used to

perform simple measurements and calculations. ABACUS is available even today for

school going children.

In the 17th century, a scientist named Pascal developed a machine that could perform

mathematical calculation. This machine comprised of a number of gears. The

movement of gear mechanism was used to perform some calculations. He named the

machine PASCALINE.

However, the concept of the modern computer was propounded by the scientist and

mathematician Charles Babbage. He first wrote on the use of logic and loops in

process execution. Based on the concept of logic and loops, Babbage envisaged two

models for performing computations- „Analytical Engine‟ and „Difference Engine‟. In

those days, electronics was not developed. Therefore, these models proposed by

Babbage existed only on paper. However, the ideas given by Babbage were

implemented after the invention of electronics.

George Boolean developed the famous Boolean Algebra based on binary numbers.

De Morgan put forward theorems on logic gates. These theorems are known as

De Morgan’s Theorems.

Lady Ada was the first computer programmer. The real application of computers

began in the late fifties. The computers were used in the United States for various

applications such as census, defense, R&D, universities etc.

Definition of a Computer

“A computer is an electronic device that can perform calculations and analysis at very

high speeds”.

Advantages of Computer

Compared to traditional systems, computers offer many noteworthy advantages. This

is one reason that traditional systems are being replaced rapidly by computer-based

systems.

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The main advantages offered by computers are as follows:

High Accuracy

Superior Speed of Operation

Large Storage Capacity

User-friendly Features

Portability

Platform independence

Economical in the long term

TYPES OF COMPUTER SYSTEMS

Computers are classified in a variety of ways depending upon the principles of

working, construction, size and applications. The following are the main types of

computer systems:

Micro Computers

Mini Computers

Mainframe Computers

Super Computers

MICRO, MINI, MAIN FRAME AND SUPER COMPUTERS

Micro Computers

Micro - Computers, now commonly called Personal Computers (PC). These are very

widely used and rapidly gaining in popularity because of the following:

Least powerful

Most widely used

Four types – 1.Desktop, 2.Notebook, 3.Tablet PC, and 4. Handheld

Figure: Micro Computers




Micro Computer market was first developed by companies like APPLE

COMPUTERS, but a key event was the launch of the IBM PC in August 1981. In the

early year of the development of the PC, the Apple Macintosh (technically not a PC)

became the standard for graphics – based applications and the IBM PC and a host of

IBM-Compatibles, were chosen for text-based (business) applications.

However, as chips have become more powerful, the difference in emphasis has

become less important. Apple has recently introduced the power PC, which is IBM-

Compatible. PCs are now the norm for small to medium-sized business computers.

Today microcomputers are Personal Computer system or stand-alone computer. They

are being distinguished from other computer systems because of possessing a single

microprocessor.

Mini Computers

These computers are also known as "Mid-Range" Computers. These are desk-sized

machines and are used in medium scale applications. For example, production

departments use minicomputers to monitor various manufacturing processes and

assembly-line operations. They are of:

Slower processing speed and less storage capacity than a mainframe

Used by medium-sized companies or departments of large corporations.

Used for specialized purposes

Figure: Mini Computers

Minicomputer is a computer whose size, speed and capabilities lie between those of a

mainframe and PC. The advent of more powerful chips now means that some 'Super

Minis' and even PCs linked in a network can run more powerfully than small

mainframe. The advent of PCs and with mainframes now being physically smaller

than in the past, the definition of a Mini-Computer has become rather vague. There is

really no definition, which distinguishes adequately between a PC and a mini

computers include IBM with its AS400, ICL and DEC.




Mainframe Computers

Mainframe Computers are next to supercomputers in terms of capacity. The

mainframe computers are multi terminal computers, which can be shared

simultaneously by multiple users. Unlike personal computers, mainframe computers

offer time-sharing.

For example, insurance companies use mainframe computers to process information

about millions of its policyholders.

The mainframes possess the followings:

Do not have as high of capacity or a fast processing as supercomputers.

Capable of storing large amounts of data.

Large corporations use them

Figure: Mainframe Computers

Mainframe Computer system is one that has at its heart a very powerful central

computer linked by cable or telecommunications to hundreds or thousands of

terminals and capable of accepting simultaneous input from all of them.

A mainframe has many times more processing power than a PC and offers very

extensive data storage facilities. Mainframe Computers are used by organizations such

as banks that have very large volumes of processing to perform and have special

security needs.




Super Computers

Super Computer is used to process very large amount of data quickly. They are

particularly useful for occasions where high volumes of calculations need to be

performed. For example in meteorological or astronomical applications,

manufacturers of super computers include Cray and Fujitsu. They are not used

commercially.

Super Computers are the most powerful computers in terms of speed of execution and

large storage capacity. NASA uses Super Computers to track and control space

explorations.

Most power type of computer.

High-capacity computers.

Fastest processing.

Used by large organizations, usually research facilities

Figure: Super Computers

ANALOGUE, DIGITAL AND HYBRID COMPUTERS

There are three basic aspects of Computers, which are Analog, Digital and Hybrid.

Analog Computers

The Analog Computer deals with quantities that are continuously variable. For

example, speedometer, electric meter, water meter, thermometer.

The computers that process analog signals are known as Analog Computers. The

analog signal is a continuous signal. For example, sine wave is an analog signal. The

analog quantities are based on decimal number systems. Examples of Analog

computers are the slide rule, ABACUS etc.




The operational amplifiers are widely used in the construction of analog computers

when the analog electrical signal is to be processed. For example, a differentiator is

the op amp circuit that differentiates input signal. If the Input signal V sin θ

to analog computer, the Output would be V cosθ.

Accordingly, the analog computer that generates the second order differential equation

can be drawn as given in the following Figure.

Figure: Analog Computers

Digital Computers

This aspect of computer operates on numbers directly. It handles numbers discretely

and precisely rather than approximately. Digital watch, Digital phone and Digital

radio are some of the examples of digital computers.

Computers that process digital signals are known as Digital Computers. The Digital

signal is a discrete signal with two states 0 and 1. In practice, the digital computers are

used and not analog. Examples of digital computers are Personal computers (PC),

Supercomputers, Mainframe computers, etc.

PC is the term referred to the computer that is designed for use by a single person. PCs

are also called microcontrollers because these are smaller when compared to

mainframes and minicomputers. The term „PC‟ is frequently used to refer to desktop

computers, Laptops, Palmtops, Personal Digital Assistance (PDA), etc. Although PCs

are used by individuals, they can also be used in computer networks.

Desktop Computer: This is the most commonly used personal computer. It comprises

of a keyboard, mouse, monitor and system unit. The system unit is also known as

cabinet or chassis. It is the container that houses most of the components such as

motherboard, disk drives, ports, switch mode power supply and add-on cards etc. The

desktop computers are available in two models- horizontal model and tower model.




Laptops: Laptops are also called notebook computers. These are the portable

computers. They have a size of 8.5 x 11 inch and weigh about three-to-four kilos.

Palmtops: Palmtops are also called handheld computers. These are computing devices,

which are small enough to fit into your palm. The size of a palmtop is like an

appointment book. The palmtops are generally kept for personal use such as taking

notes, developing a list of friends, keeping track of dates, agendas etc. The Palmtop

can also be connected to a PC for downloading data. It also provides value-added

features such as voice input, Internet, cell phone, camera, movie player and GPS.

Personal Digital Assistant (PDA): PDA is the palm type computer. It combines pen

input, writing recognition, personal organizational tools and communication

capabilities in a small package.

Hybrid Computers

This computer combines the features of both analog and digital computers. They

handle data in both quantities and variable

BUSINESS AND SCIENTIFIC COMPUTER SYSTEMS

There are two basic types – special and general-purpose computer

Special Purpose Computer: This aspect of computer is designed to perform one or

specific task. The program of this aspect of computer is in-built into the machine

permanently. For instance, special purpose computers are used for solving navigation

problems in aircraft and ships.

General Purpose Computer: These computers have the ability to handle a wide variety

of different programs and to solve many different problems.

Types of Application

There are two types – Scientific and Business Applications.

Scientific Applications: These computers are designed to handle scientific

application more effectively. They require small volume of data input and

output.

Business Data-Processing Application: These computers are designed to handle

business data processing applications. They need a large data file, input

storage, output storage devices and large storage capabilities.

Practical Data Processing Applications in Business

The following are some data processing information undertaken by commercial

organizations:

1. Process Control: In production process, a computer is directly connected to

some plant to control and monitor it. Here, the computer receives the data

directly from the plant.




2. Accounting: The data processing system can be used to maintain the accounting

records and in preparation of final accounting. The general ledger, accounts

payable, accounts receivable, etc.

3. Payroll Preparation: In personnel department the data processing system is used

to record the operations of the number of employees of different departments in

each shifts, leave taken, deductions such as ESI, PF and finally in the

preparation of pay slips.

4. Inventory Management: Data processing is used to maintain up-to-date

information about stock, their costs and to initiate orders when the times are

about to be exhausted.

5. Office Automation: The modern offices and business organizations are

dependent upon computer based office automation for their competitiveness

and better management.

6. Banking and Insurance: Automatic Teller Machines are placed in big cities and

linked to central computers. Hence the delay in processing is completely

avoided.

7. Managerial Aid: The data processing system is used as a managerial aid in

decision-making for solving business problems. It is also very useful in the area

of linear programming, PERT, CPM, etc.

Data Processing Operations

The data after some processing is transformed into information which is organized and

meaningful. It includes the following operations:

Data Generation: It involves the operation of collecting the original data. It

implies that the raw data are collected and set out in the form of original

document called a source document.

Recording: Here raw data are converted into an acceptable form. That is, the

data is transcribed from the source documents on the cards or on some other

specified forms and are made readable for the machines.

Verification: After the data have been recorded, their accuracy has to be

checked. This can be done with the help of another machine called verifier or

by re-reading.

Classification: Classification of information is the next important operation in

which the data is separated into various categories.

Sorting: Sorting involves sequencing the data in a pre-determined order to

facilitate processing. The order may be either alphabetic or numeric.

Merging: It is the operation of combining two or more ordered (sorted) sets of

data to form another single ordered set.

Calculating: Here calculation of greater magnitude can be processed.

Calculation involves solving equations and manipulations of the sourced data

such as addition, subtraction, etc.

Data Storage: The data is stored in a location called memory referred by its

address. In large organizations, huge volume of data is to be stores and

accessed. Hence some auxiliary storage devices are also needed for the

effective data processing.




Memory is measured by the following units:

(a) BIT (Binary Digit) – It is the smallest possible unit of information. It can be

either 0 or 1.

(b) NIBBLE – Four bits form one nibble

(c) BYTE – It is a unit of information consisting of fixed numbers of bits. It is

a combination of 8 bits.

(d) CHARACTER – It is represented by one byte. It can be a letter, digit,

punctuation mark or special character.

(e) WORD – The combination of 2 bytes or 4 bytes or 8 bytes is a word.

The data measurement is as follows:

8 bits – 1 byte

1024 bytes – 1 kilobyte (KB)

1024 KB – 1 Mega Byte (MB)

1024 MB – 1 Giga Byte (GB)

1024 GB – 1 Tetra Byte (TB)

(f) SECONDARY STORAGE (Backing /Auxiliary Storage)

(i) Magnetic disk – It includes the following.

(ii) Hard disk – Rigid, Floppy disk – Flexible

(iii) Magnetic tape

(iv) Magnetic drum

(v) Mass storage device – cartridge

(vi) Optical disks – CD ROM (Compact Disk – ROM)

Data Retrieving: The process of searching or locating a data item from the

storage is data retrieving. In EDP (Electronic Data Processing) system, the data

is retrieved from the storage device in sequential, indexed sequential or random

access mode.

Reporting: The processed information may be reported in a number of ways

depending on the use of results. The results may be printed out in the form of

pay slips, bills, etc. or other types of reports.

FIRST, SECOND, THIRD AND FOURTH GENERATION COMPUTERS

Generations of Computers

Generation in computer terminology is a change in technology a computer is/was

being used. Initially, the generation term was used to distinguish between varying

hardware technologies. But nowadays, generation includes both hardware and

software, which together make up an entire computer system. Using size and features

as the bases, computers are classified into various generations.

FIRST GENERATION

(The period of first generation: 1946-1959: Vacuum tube based)

The first generation computers were bulky in size. They were able to executehundreds

of instructions per second and were expensive as well. They used vacuum tubes as

their main components. Machine language is a first generation language, for example

EDVAC, UNIVAC etc.




SECOND GENERATION

(The period of second generation: 1959-1965: Transistor based)

The second-generation computers were smaller in size as compared to the first

generation computers. These were capable of executing thousands of instructions per

second, with a transistor as its main component. Assembly language is the second

generation language in which programs were written using mnemonic codes, for

example, PDP (Programmed data processor), PDP1 etc.

THIRD GENERATION

(The period of third generation: 1965-1971: Integrated Circuit based)

The third generation computers were more advanced and used integrated circuits.

These computers contained thousands of components per circuit. They were cheaper

than second-generation computers. The languages used in this generation were

BASIC, COBOL etc. for example, IBM 307 Series, PDP II etc.

FOURTH GENERATION

(The period of fourth generation: 1971-1980: VLSI microprocessor based)

The fourth generation computers used complex circuits like the large-scale integrated

circuits called microprocessors or chips, which surprisingly cost less than the third

generation computers. These computers were able to execute millions of instructions

per second. The languages used in this generation are C++, SQL etc. for example,

CRAY 2, IBM 3090/600 Series.

FIFTH GENERATION

(The period of fifth generation: 1980-onwards: ULSI microprocessor based)

These computers work on artificial languages (AI) like LISP, PROLOG etc. They use

super/ultra-large-scale integrated circuits, which is also called parallel processing

method. They execute billions of instructions per second, for example, Laptops,

Palmtops, PDA (Personal Digital Assistant) etc.

Computer Generations

S.No. Generation & Description

1 First Generation

The period of first generation: 1946-1959. Vacuum tube based

2 Second Generation

The period of second generation: 1959-1965. Transistor based

3 Third Generation

The period of third generation: 1965-1971. Integrated Circuit based

4 Fourth Generation

The period of fourth generation: 1971-1980. VLSI microprocessor based

5 Fifth Generation

The period of fifth generation: 1980-onwards. ULSI microprocessor based




First Generation Computers - The period of first generation was 1946-1959.

The main features of First Generation are:

1) Vacuum tube technology

2) Unreliable

3) Supported Machine language only

4) Very costly

5) Generate lot of heat

6) Slow Input/ Output device

7) Huge size

8) Need of A.C.

9) Non-portable

10) Consumed lot of electricity

Some computers of this generation were:

a) ENIAC

b) EDVAC

c) UNIVAC

d) IBM-701

e) IBM-650

Second Generation Computers – The period of second generation was 1959-1965

The main features of Second

Generation are:

1. Use of transistors

2. Smaller size as compared

3. Generate less heat as compared

4. Consumed less electricity

5. Faster than first generation

6. Still very costly

7. A.C. needed

8. Support machine and assembly

languages

Some computers of this generation

a) IBM 1620

b) IBM 7094

c) CDC 1604

d) CDC 3600

e) UNIVAC 1108




Third Generation Computers – The period of third generation was 1965-1971

The main features of Third

Generation are:

• IC used

• More reliable

• Smaller size

• Generate less heat

• Faster

• Lesser maintenance

• Still costly

• A.C. needed

• Consumed lesser electricity

• Support high-level language

Some computers of this

generation were:

• IBM-360 series

• Honeywell-6000 series

• PDP(Personal Data Processor)

• IBM-370/168

• TDC-316

Fourth Generation Computers– The period of Fourth Generation was 1971-1980

The main features of Fourth

Generation are:

• VLSI technology used

• Very cheap

• Portable and reliable

• Use of PC's

• Very small size

• Pipeline processing

• No A.C. needed

• Concept of internet was

introduced

• The fields of networks

•Became easily available

Some computers of this

generation were:

• DEC 10

• STAR 1000

• PDP 11

• CRAY-1 (Super Computer)

• CRAY-X-MP (Super Comp)




Fifth Generation Computers – The period of Fifth Generation is 1980-till date.

The main features of Fifth

Generation are:

• ULSI technology

• True artificial intelligence

• Natural language processing

• Advancement in Parallel

Processing

• Advancement in

Superconductor technology

• More user friendly interfaces

with multimedia features

• powerful and compact

computers at cheaper rates

Some computers types of this

generation are:

• Desktop - Laptop

• NoteBook – UltraBook

• ChromeBook

Nowadays, we see languages that are both safe and powerful. Sometimes we have to

use assembly language (Low-Level Language, LLL) because there is just no other

reasonable way of telling the computer what it must do. However, most programming

is done in High-Level Languages (HLLs) because of productivity. It is usually easier,

or more cost-effective, to use a HLL. Some of the reasons for this are:

Easy to write : Useful concepts and facilities, relevant to application

Easy to read : For reuse, maintenance, enhancement etc.

Portability : Other compiler/toolset suppliers, users, computers - standards

Error detection and reporting

LAPTOP OR NOTE BOOK COMPUTERS

The original portable computers were heavy; weighing around five kilograms and

could only be run from the main electricity supply. Subsequent developments allow

the true portability.

Laptop is powered either from the electricity supply or using a rechargeable

battery. It uses31/2 disks and CD-ROMs, a liquid crystal or gas plasma screen

and is fully compatible with desktop PCs.

The Notebook is about the size of an A4 pad of paper. Some portables are now

marketed as „sub-notebooks'.




A laptop, often called a notebook, is a portable personal computer with a clamshell

form factor, suitable for mobile use. Although originally there was a distinction

between laptops and notebooks, the former being bigger and heavier than the latter, in

modern usage there is often no longer any difference. Laptops are commonly used in a

variety of settings, such as at work, in education, and for personal multimedia.

A laptop combines the components and inputs of a desktop computer, including the

display, speakers, a keyboard, and pointing devices (such as a touchpad or track pad)

into a single unit. Most modern-day laptops also have integrated webcams and built-in

microphones.

Portables computers which later developed into modern laptops, were originally

considered to be a small niche market, mostly for specialized field applications, such

as in the military, for accountancy, or for sales representatives. As portable computers

became closer to the modern laptop, they became widely used for a variety of

purposes

Among the best-known makers of notebook and laptop computers are IBM, Apple,

Compaq, Dell, Toshiba, and Hewlett-Packard

DATA PROCESSING SYSTEMS

A Data Processing System is a combination of machines, people, and processes that

for a set of inputs produces a defined set of outputs. The inputs and outputs are

interpreted as Data, facts, information, depending on the interpreter's relation to the

System. A common synonymous term is "information system".

Data means any collection of raw figures facts. Data can be considered as the raw

material of information. The data may be numerical such as payroll, employee

number, etc. or non-numerical like student names, product names, etc.

Data Processing

As data in its raw form it cannot solve any problem. The data needs some processing

to make it useful. Data processing is the conversion of data into a more useful form.

That is, transmission of data into meaningful information is called data processing.

Information

The result obtained by data processing is called information. That is, the processed

data is known as information. However, information produced in one data processing

step may be used as data in the next data processing step.

Data Versus Information

Data Information

Raw records Completed one

Un ordered Ordered

Unrefined data Refined data

What prevails? What is necessary?




Data Processing System

Data processing is viewed as a system that accepts data as input, process it into

information as output. This can be explained with the help of the following diagram.

Figure: Data Process

Data Processing Cycle

Once data is collected, it is processed to convert it into useful information. The data is

processed again and again until the accurate result is achieved. This is called data

processing cycle.

The data processing is very important activity and involves very careful planning.

Usually data processing activity involves three basic activities – Input, Processing,

and Output

Data Processing Activities

Regardless to the type of equipment used, various functions and activities which need

to be performed for data processing can be grouped under five basic categories:

Figure: Data Processing Activities

Types of Data

Data is divided into two types: (1) Numeric Data and (2) Character Data

1. Numeric Data: The data which is represented in the form of numbers is known

as numeric data. This includes 0-9 digits.

2. Character Data: Character data falls into two groups: (a) String data and (b)

Graphical data.

String data consists of the sequence of characters. Characters may be English

alphabets, numbers or space. The space, which separates two words, is also a

Collection

Originating

Measuring

Recording

Comparing

Conversion

Coding

Classifying

Verifying

Transforming

Manipulati

on

Storing

Calculating

Summarizing

Comparing

Storage

Storing

Retrieving

Communic

ation

and

Reproduction




character. The string data is further divided into two types – Alphabetic data

and alphanumeric data.

Graphical data it is possible that pictures, charts, and maps can be treated as

data. The scanner is normally used to enter this type of data. The common use

of this data is found in the National Identity Card.

Types / Kinds of Data Processing

The important kinds of data processing are as follows:

1. Manual Data Processing: Data is processed without the help of mechanical

devices. Here the data is processed using manual things such as abacus, slide

rule, Napier bones etc.

2. Mechanical Data Processing: Data is processed through mechanical devices like

calculators, tabulators, etc. are used for processing.

3. Electronic Data Processing: Data is processed by either analog or digital

computer.

Objectives of Data Processing

Handle Huge Volume of Data: The basic objective of data processing is to

handle huge data in order to enable the organization to function efficiently.

Qualitative and Quantitative Information: The next important want of data

processing is to provide qualitative and quantitative information.

Proper and Timely Information: Different kinds of information are needed in

almost all organizations. Data processing provides correct and timely

information.

Storage and Retrieval of Data: Through data processing, information can be

stored and retrieved as and when necessary.

Helps in Decision-making: In every organization various decisions are taken at

different levels. Such decisions can be more accurate if effective data

processing system is used.

Improves Productivity: To improve productivity, various measures are to be

identified and implemented. It is possible through the properly designed data

processing system

Maintaining Performance at Optimum Level: There should be a smooth flow of

information among various functional departments. This can be easily achieved

through data processing system.

Efficient Office Management: In office management also data processing plays a

very important role, through which office automation can be done.

Steps in Data Processing

1) Identifying the Data

2) Input of Data

3) Manipulation of Data

4) Output of Information

5) Storage of Information




Step 1: Identifying the Data: The first step in data processing is to locate necessary facts

and figures from source documents. Accurate, relevant and adequate data must be

used as input.

Step 2: Input of Data: After extracting the necessary data from the source documents,

they must be transposed in a suitable form acceptable to the computer. Great care

should be taken to avoid wrong entries in the forms.

Step3: Manipulation of Data: It involves the process of shifting, sorting and rearranging

the given input. Before processing, validation procedures may be built in to the code

to so that input forms do not accept any incorrect data.

Step 4: Output of Information: The main purpose of data processing is to provide

meaningful information o the decision-maker. Hence, in data processing the person

involved must be very careful about what information is needed and in what form he

likes to have it.

Step 5: Storage of Information: The data processed need to be kept for future use. All

the processed data will need some form of secondary storage. When storing the data, it

is always important to maintain a backup.

BATCH-ONLINE AND REAL TIME SYSTEMS

Batch Processing

In a batch processing group of transactions collected over a period of time is collected,

entered, processed and then the batch results are produced. Batch processing requires

separate programs for input, process and output. It is an efficient way of processing

high volume of data. For example: Payroll system, Examination system and Billing

system.

Definition: To process a large set of data in a specific way, automatically,

without needing any user intervention. The data is first collected, during a work

day, for example, and then batch-processed, so all the collected data is

processed in one go. This could happen at the end of the work day, for

example, when computing capacities are not needed for other tasks.

Advantages: It is possible to perform repetitive tasks on a large number of

pieces of data rapidly without needing the user to monitor it.

Interactive (or) Online Processing

Definition: Data is processed immediately while it is entered, the user usually

only has to wait a short time for a response. (For example, games, word

processing, booking systems). Interactive or online processing requires a user

to supply an input.

Advantages: Interactive or online processing enables the user to input data and

get the results of the processing of that data immediately.

Real time Processing

In real time processing, there is a continual input, process and output of data. Data has

to be processed in a small stipulated time period (real time) otherwise it will create




problems for the system. For example, when a bank customer withdraws a sum of

money from his account it is vital that the transaction be processed and the account

balance updated as soon as possible. Also airline reservation is an example.

Real time processing is a subset of interactive or online processing.

Definition: Input is continuously, automatically acquired from sensors, for

example, which is processed immediately in order to respond to the input in as

little time as possible. After the system is finished responding it reads the next

set of input data immediately to process that. This system doesn't need a user to

control it, it works automatically.

Advantages: Whenever there is a rapid reaction required due to some sort of

change, real time processing can take action without the need of a user or long

processing time beforehand.

Real-time Applications

In real-time applications, computers control an on-going activity. Let us consider the

example of a manufacturing process. A product C is made from raw materials A and

B. The quality of C depends upon, among other things, the quality of A and B and

their quantities. In big manufacturing process, raw materials are fed by machineries.

Due to problems in machineries, the performance may vary from machine to machine.

This affects the quality of final product.

Manual inspection of quality and operation of these machineries to control the

quantity are slow. This slows the manufacture of C from raw materials A and B.

Signals from C are fed to the computer. Suitable sensors are installed in the lines

carrying raw materials as well as finished product. These generate signals.

TIME SHARING SYSTEMS

In computing, time-sharing is the sharing of a computing resource among many users

by means of multiprogramming and multi-tasking. Its introduction in the 1960s by

students and professors at Dartmouth College, and emergence as the prominent model

of computing in the 1970s, represented a major technological shift in the history of

computing.

By allowing a large number of users to interact concurrently with a single computer,

time-sharing dramatically lowered the cost of providing computing capability, made it

possible for individuals and organizations to use a computer without owning one, and

promoted the interactive use of computers and the development of new interactive

applications.

Time-sharing was developed out of the realization that while any single user would

make inefficient use of a computer, a large group of users together would not. This

was due to the pattern of interaction: Typically an individual user entered bursts of

information followed by long pauses but a group of users working at the same time

would mean that the pauses of one user would be filled by the activity of the others.




Given an optimal group size, the overall process could be very efficient. Similarly,

small slices of time spent waiting for disk, tape, or network input could be granted to

other users.

MULTI PROGRAMMING AND MULTI PROCESSING SYSTEMS

Multiprogramming Operating Systems

Multiprogramming is also the ability of an operating system to execute more than one

program on a single processor machine. More than one task/program/job/process can

reside into the main memory at one point of time.

Example: A computer running Excel and Firefox browser simultaneously is an

example of multiprogramming.

Multitasking is the ability of an operating system to execute more than one task

simultaneously on a single processor machine. Though we say so but in reality no two

tasks on a single processor machine can be executed at the same time. Actually CPU

switches from one task to the next task so quickly that appears as if all the tasks are

executing at the same time. More than one task/program/job/process can reside into

the same CPU at one point of time.

Multiprocessing Operating Systems

Multiprocessing is the use of two or more processing units within a single computer

system. The Multiprocessing operating system provides for the use of multiple

processors. These operating systems enable several programs to run concurrently.

These are much more complicated than single-process systems because the operating

system must allocate resources to completing process in a reasonable manner.

Examples: UNIX, Windows 2000, Windows XP Professional, and Windows Server

2003 are examples of operating systems than can use multiple processors.

Multiprocessing is the ability of an operating system to execute more than one process

simultaneously on a multi-processor machine. In this, a computer uses more than one

CPU at a time.

Graphical User Interface Operating Systems (GUI)

The Graphical User Interface operating systems are the operating systems having the

capability of using graphical elements. For the users interface a mouse is also attached

to GUI Operating Systems are much easier for end-users to learn and use because

commands do not need to be known or memorized. Because of their ease of use, GUI

operating systems have become the dominant operating system used by end-users

today.

Examples for the GUI operating systems include Microsoft Windows, Mac OS X, etc.




Single-User Operating System

Single-user operating system provides access to the computer system by a single user

at a time. If another user needs access to the computer system, they must wait till the

current user finishes what they are doing and leaves.

Examples: Microsoft Windows, Apple Mac OS X are the common example for this

category.

Multi-User Operating System

The multi-user operating systems allow multiple users to utilize the system resources

simultaneously and run programs at the same time. That is, it allows concurrent access

by multiple users and work at the same time. Access to the computer system is

normally provided via a network, so that users access the computer using a terminal.

Examples of multi-user operating systems are UNIX, Linux and in Windows early

version where single user and later i.e. after Windows NT, Microsoft Windows 2000,

Windows Server 2003, Windows Server 2008, Windows HPC Server 2008, Windows

Server 2008 R2, Windows Server 2012 are multi-user operating systems.

Multithreading Operating System

Multithreading means subdividing the specific operations within a single program /

application into individual threads. The parts or divisions of the program / application

are called threads. Multithreading operating systems allow different parts of a

software program to run parallel. The operating system allocates the processing time

not only among different applications, but also among each thread within an

application.

Example: Operating systems like Windows XP /2000, Solaris, Linux, Tru64 UNIX,

Max OSX support multithreading.

NET WORKING – LOCAL AREA AND WIDE AREA NET WORKS

Computer Networks

A computer network is an interconnection of computer systems located at different

places. It is a set of devices known as nodes, terminals or work stations interconnected

by communication links. Computers are linked together for the purpose of

communicating data and sharing resources.

The computer that provides resources to other computers on a network is known as

server. In the network the individual computers, which access shared network

resources, are known as nodes.

Network can be defined as “an interconnected group of independent computing nodes

which have the characteristics of:

(a) Well-defined, mutually-agreed set of rules and conventions called protocols or

set of rules




(b) Interaction with one-another by authorization

(c) Facilitating resources-sharing in controllable manner”.

Need for Computer Networks

Computer networks are used in almost all types of organizations. The following main

reasons for the networking:

File Sharing: The data files and other resources electronically are centralized in

one place of the organization, then, it is much easier for the concerned people

to share documents and other data.

Hardware Sharing: In networking environment, the users can share hardware

devices such as printers, scanners, CD drivers, hard drivers, etc.

Application Sharing: Applications can be shared over the network and this

allows implementing client / server applications.

User Communication: Networks allow users to communicate using e-mail,

news, groups, and video conferencing etc.

Cost Reduction: Networking results in cost reduction by sharing hard-and

software resources in the organizations.

Reliability and Flexibility: Networking is highly reliable and flexible.

Communication and Collaboration: Networking allows employees to share files,

and share comments on work done by others in the network and suggest

measures in case of errors etc.

Components of a Network

Network is nothing but techniques, physical connections, and computer programs used

to link two or more computers. Network users are also share files, printers and other

resources; send electronic messages; and run programs on other computers.

A network has three layers of components:

1. Application Software

2. Network Software

3. Network Hardware

Application Software: Application Software consists of computer programs that

interface with network users and permit the sharing of information and resources.

One type of application software is called client-server. Client computers send

request for information or requests to use resources to other computers, called

servers that control data and applications.

Another type of application software is peer-to-peer. In peer-to-peer network,

computers send messages and requests directly to one another without a server

intermediary.

Network Software: Network software consists of computer programs that establish

protocols, or rules, for computers to talk to one another. These protocols are carried

out by sending and receiving formatted instructions of data called packets. Protocols

make logical connections between network applications, direct the movement of




packets through the physical network, and minimize the possibility of collisions

between packets sent at the same time.

Network Hardware: Network hardware is made up of the physical components that

connect computers. Two important components are the transmission media that carry

the computers signal, typically on wires or fiber-optic cable, and the network adapter,

which accesses the physical media that link computers, receives packets from network

software, and transmits instructions and requests to other computers. Transmitted

information is in the form of binary digits (1s and 0s), which the computer‟s electronic

circuitry can process.

Network Connections

A network has two types of connections

1. Physical Connections: Physical connections let computers directly transmit and

receive signals and logical. Physical connections are defined medium by the

used to carry the signal, the geometrical arrangement of the computers and the

method used to share information.

2. Virtual Connections: Virtual connections allow computer applications, such as

word processors, to change information. Logical connections are created by

network protocols and allow data sharing between applications on different

types of computers in a network.

Some logical connections use client-server application software and are primarily for

file and printer sharing.

Types of Computer Networks

NETWORK BASED ON GEOGRAPHICAL LOCATIONS

The networks can be classified on the basis of geographical area covered as follows:

Local Area Network

A local area network (LAN) is group of computers and associated devices that share a

common communication line and typically share the resources of a single processor or

Types of Networks

On the basis of Geographical

Area Covered

On the basis of Nature and

Scope

Local Area Network

Wide Area Network

Metropolitan Area Network

Wireless Local Area Network

Intranet

Extranet

Internet




server within a small geographic area (for example, within an office building). Usually

the server has applications and data storage that are shared in common by multiple

computer users. A local area network may serve a few as two or three users (for

example, in a home network) or may as thousands of users.

Features of Local Area Network

a) Inexpensive transmission media

b) Inexpensive devices (modems, repeaters and transceivers) to interface to the

media

c) Easy physical connection of devices to the media

d) High data transmission rates

e) Network data transmissions are independent

f) A high degree of interconnection between devices

Types of LAN Connections

1. Internal LAN Connections: The physical connection LAN devices can be

coaxial cable, pairs of copper wires, or optical fiber. Wireless connections also

can be made using infrared or radio-frequency transmissions.

2. External LAN Connections: Connections that link LANs to external resources,

such as other LANs or remote databases, are called bridges, routers and

gateway.

A bridge creates an extended LAN by passing information between two

or more LANS.

A router is an intermediary device that connects a LAN to a larger LAN

or to a WAN by interpreting protocol information.

A gateway connects and translates between networks that use different

communications protocols.

A special type of gateway called a firewall keeps external users from

accessing resources on the LAN to access external information.

Structure of Local Area Network

The following are the important LAN – structures:

1. Bus Network

2. Star Network

3. Ring Network

4. Token Ring Network

5. Hierarchical Network

Bus Network: It is a configuration for a local area network in which all nodes

are connected to a main communication line (bus). On a bus network, each

node monitors activity on the line.

Star Network: It is a local area network in which each device (node) is

connected to central computer in a star-shaped configuration (topology);

commonly, a network consisting of a center computer (the hub) surrounded by

terminals.




Ring Network: It is a local area network in which devices (nodes) are connected

in a closed loop, or ring. Messages in a ring network pass in one direction, from

node to node.

Token Ring Network: It is a local area network in ring topology in which all the

computers are arranged in a circle. A token is a special bit pattern and it travels

around the circle. Token governs the right to transmit is passed from one

station to the next in a physical circle.

Hierarchical Network: They are configured to have multiple levels of systems

interconnected with one another. A large system interconnection is with several

other systems. Each lower level interconnects additional systems terminals.

Wide Area Network

Wide area network include all the networks which are involved in transporting

information from one geographic location to another. The scale is much greater than

in local networks. A wide area network will almost always by employed whenever the

information is electronic from one cable leaves the site, even it is only to cross over

the street another building.

Features of Wide Area Network

A wide area network (WAN) is used to connect LANs and nodes that are separated by

great physical distance. Generally speaking it is larger version of LAN with several

differences:

a) It operates by means of the international telephone network.

b) Unlike LANs which owned by their users, WANs operate on public and leased

telephone lines, satellite and microwave, which are regulated by governmental

agencies.

c) Data transmission is somewhere slower.

d) The WAN compose any of the system configurations such as Single Nodes,

Clusters, and LANs.

Suppose a company has its central headquarters in Coimbatore and the Coimbatore

site contains all department and equipment for product manufacturing product

distribution, accounting and sales. The information pertaining to these operations is

tracked by a single centralized database system.

As the company becomes more profitable and expands, it established additional sales

offices on Mumbai and Delhi. Each sales office maintains its own system to record

and track customer orders for its region. At the same time the two sites are linked to

the mode at corporate headquarters and relay each order for shipment and inventory

and invoice processing.

Metropolitan Area Network

A MAN (metropolitan area network) is a network that interconnects users with

computer resources in a geographical area or region larger than covered by even a

large local area network but smaller than the area covered by a wide area network.

The term is applied to the interconnection of networks in a city into a single larger




network. It is also used to mean the interconnection of several local area networks by

bridging them with backbone lines. The latter usage is also sometimes referred to as a

campus network.

Wireless Local Area Network

Wireless LANs uses radio frequency for transmit and receive data using air as a

medium. In typical WLAN setup a transmitter/receiver device, known as access point,

connects to wire network from a fixed location using standard cable. Access point

receives buffers and transmits data between WLAN and wired network infrastructure.

A single access point can support small number of user and function within a range of

one hundred to several hundred feet. End users can access WLAN through wireless

LAN adapter (network card) which is most famous a PC card / PCMCIA card in

notebooks or palmtop computer.

Technologies of WLAN

Narrow Band: A narrow band radio system transmits and receives information

on a specific radio frequency (RF). Narrow band keeps the frequency as low as

possible just to pass the information for security purpose and avoiding cross

talk.

Spread Spectrum: Most WLAN systems use spread-spectrum technology,

developed by military for the use in reliable, secure, mission-critical

communication systems. As compared to narrow band, spread-spectrum

consumes more bandwidth but provide more security.

Infrared: IR (Infrared) use very high frequency, just below visible light to carry

data. IR cannot penetrate the opaque object. It is generally used for personal

area network and can function efficiently within the range of three feet.

NETWORK BASED ON NATURE AND SCOPE

On the basis of nature and scope, the networks can be classed as Intranet, Extranet,

and Internet.

Intranet

An Intranet is a private network that is maintained within an enterprise. It may consist

of many interlinked local area networks and also use leased lines in the wide area

network. It can be used to access one or more internal website, which are located

centrally or distributed among departments or divisions. This includes integration of e-

mail, FTP, mail server and web servers with the internal applications. Web browsers

provide user interface.

Thus, Intranet can be defined as “a computer network connecting an affiliated set of

clients using standard internet protocols and an IP-based network of nodes behind a

firewall, connected by secure networks”.

Features of Intranet

a) It is the use of internet technologies for internal networks.




b) It uses TCP/ IP, hypertext transfer protocol and other internet protocols.

c) It integrates the mail, file, and web, audio and video services.

d) It is accessible only by the organization‟s members.

e) It is not limited by physical locations.

f) It is protected by firewalls.

Types of Intranet

1. Human Resource Intranet

2. Sales and Marketing Intranet

3. Information System Intranet

4. Executive or Corporate Intranet

5. Customer Service Intranet

6. Finance Intranet

Extranet

An Extranet is a private network that uses the internet protocol and the public

telecommunication system to securely share part of business information or operations

with suppliers, vendors, partners, customers, or other business. An Extranet can be

viewed as part of a company‟s intranet that is extended to users outside the company.

It has also been described as a “state of mind” in which the internet is perceived as a

way to do business with other companies as well as to sell products to customers.

Extranet extends the intranet from one location to another across the internet by

securing data flow, to another intranet of a business partner. In these way intranets of

business partners, suppliers, creditors, distributors, customers, and the lines are

connected to extranets by agreements.

An extranet requires security and privacy. These require firewall server management,

the issuance and use of digital certificate or similar means of user authentication,

encryption of messages, and the use of virtual private networks that tunnel through the

public network.

Characteristics of Extranet

a) It is an extended internet-private business networks located outside of the

corporate firewall.

b) It can be referred to an intranet that is partially accessible to authorized

outsiders.

c) It is a network that uses the internet to link business with others that share the

common goals.

Internet

The internet is a worldwide system of computer networks – a network of networks. It

is a means of connected a computer to any other computer anywhere in the world via

dedicated routers and servers. It is a worldwide public network of computers on which

people can join and use multiple services such as sharing of information.




When two computers are connected over the internet, they can send and receive all

kinds of information such as text, graphics, voice, video, and computer programs. It

consists of millions of private, public, academic, business and government networks at

global level and is linked by a broad array of electronic and optical networking

technologies.

INTERNET VS INTRANET

Parameter The Internet An Intranet

Security Low or None High

Speed Low or Medium High

Services Almost unlimited Specified by organization

Access Control None or Limited. Public

encourage to visit

Account Name and Password.

Generally no external (public)

access.

Membership Unlimited Population of organization

Reliability Low High

Control Low or None High

Size Enormous Constrained Small, Medium or

Large

Costs Attachment: Low Presence:

Medium

Medium to High

Benefits What we see is what we get Efficiencies and Productivities

Text Books & References

1. Dr.R.Parameswaran, “Computer Applications in Business”, S.Chand & Company

Pvt.Ltd, New Delhi, 7th

Edition, 2014.

TEXT BOOKS:

1. John Shelley, Hunt Roger, 1987. Computer and Commonsense Business data processing. Edition, 3, Publisher, Prentice-Hall of India.

2. Brightman and Dimsdale, 2000. Using Micro Computers. Golgotha Publishers, Delhi. REFERENCE BOOKS:

1. Faxali R.K, 2004. PC Software Made Simple. Tata McGraw Hill Publishing, Second Edition. 2. Alexis and Mathews Leon, 2001. Introduction to Computers. Vikas Publishing House Pvt.

Ltd. 3. Henry Clucas, 2009. Information Technology for Management. McGraw-Hill / Irwin


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Education