UNIT-I

HARDWARE AND SOFTWARE :

Hardware:

The physical and tangible components which are seen and touched in a computer such as electrical and electronic units are known as hardware of the computer. That is input units, Output units, CPU and Backing storage are called Hardware.

Input devices – Keyboard, Mouse, Joystick, Light pen etcOutput Devices – Visual Display Unit (VDU), Printer etcSecondary storage units – Magnetic Disk, Magnetic Tape, Floppy Disk Drive etc

Software:

A computer is directed to perform input, arithmetic, logical, output and storage operations by a series of instructions called a computer program. A computer program specifies what operations are to be performed and the sequence in which they are to be performed. The program should be in the main memory for its execution. Computer programs are commonly referred to as ‘computer software’.

Software activates the hardware. Software is developed by human thinking whereas the hardware is developed by the technological improvement. Generally software means all the computer programs associated with a computer system like compiler, assembler etc.

Computer software can be broadly classified as: Application Software System Software

The application software refers to a collection of programs meant for a specified application. E.g.: programs for Payroll, Inventory etc.,System Software deals with programs concerned with the system E.g.: Assembler, Compiler, Linker etc.

COMPUTER SYSTEMS:

Definition:

Computer is an electronic data processing (EDP) device, which accept data From the keyboard, process the data as per instructions given and produces the output.

Characteristics/Advantages of Computers:

(1) Speed: A computer is a very fast device that can perform an amount of work that human being can do in months. Since all operations of the computer are fast , they can perform large number of operations in a second. The processing speed of the computer is measured by nano seconds (1 nano sec is 1 billion of a second), Small computers take a few micro seconds to execute an operation. Whereas large computer takes only few nano seconds for the same operation.

(2) Accuracy:

The next very important characteristic of a computer is its accuracy. It is estimated that a human being commits at least one error for every thousand operations but computers do millions of operations in a second committing no errors. If the output is not correct then it is not the computer’s mistake, it is due to the input error, if the data and instructions are given correctly to the computer it will give accurate information.

(3) Memory Capacity: It can store large amount of data and information, which is expressed in terms

of Kilobytes. This memory capacity can be increased by using secondary storage devices such as floppy disk, optical disk etc.

Bit -> 0, 11 byte ->8 bits1 KB ->1024 byte1 MB ->1024 KB1 GB ->1024 MB1 TB ->1024 GB

(4) Automation:

The computers execute the program completely without human instruction until completion. If we want to repeat the same process for another set of data there is no need to feed the program once again but we have to give execution command once again.

(5) Versatile :

Computer is a versatile machine and is capable of solving any problem and can be applied to all sorts of business and other activities.

Example: Computers are used in banks, education, preparing electric bills, telephone bills, reservations etc.

(6) Diligence: Computer being a machine wont suffer from tiredness and lack of concentration. The computers can work for hours together but a human being becomes tired after a certain time.

Disadvantages:

(1) The intelligence of the computer is zero. Computer is an obedient servant to its master and work according to his command.

(2) The computers will not correct logical errors.

(3) Lacks commonsense

(4) It has to depend upon programmer’s instructions.

IMPORTANCE OF COMPUTERS IN BUSINESS:

In the modern business world, it is not unusual for the computer to be used by management personnel at all levels to aid in decision making; by office workers in all

departments for automating the tasks of preparing documents, filling documents, retrieving data, and communicating information to others throughout the company and by personnel in the manufacturing and production departments for tasks varying from automated assembly by computerized robots to controlling shipping and warehouse scheduling. Most jobs in modern companies require some knowledge and use of computers.

The needs of the computer user fall into three broad categories: Information Management Management Support Function Support

Information Management refers to the task of managing and controlling the data and information required within an organization for that organization to function.Management support consists of those activities carried out within a company to supply management personnel with information on which decisions can be made and action taken. Systems that provide management support are sometimes known as Decision Support System.Function support refers to the use of the computer by people to perform their jobs faster; more efficiently, and with less cost to the company.

Three ways, in which individuals can meet their information management, management support and function support are

(1) Uses of Personal ComputersPersonal computers are widely used in the business environment by personnel at all levels. Personal computers are often used in conjunction with specialized software packages that have gained almost universal acceptance.These packages include:

Word Processing S/W – used to write letters, memos and other documents. Electronic Spreadsheets S/

W-used for calculations using formulas Computer Graphics S/W-trans forms

the series of numeric values into a graphic form Database and File Management S/W-allows user to access data at any

required form Electronic main S/W-lets users to communicate with each other via their

personal computer network.

(2) Use of Information Centers

A second major way for users to obtain access to computing power isThrough the use of an information center. An information center is an area within the information systems department that contains a number of CRT terminals, hardcopy generators (usually printers), and perhaps a smaller computer. These devices have direct access to a centralized computer in the information systems department.

The major reason for an information center is to give employees a simple, effective way to meet their own departmental and individual information processing needs. This is accomplished by providing computing power, training and access to sophisticated software so users can generate their own reports and develop their own applications. Thus, the information center provides more sophisticated hardware and software than personal computers. The information center’s main goal is to provide extensive computer processing for computer users.

(3) Use of a Centralized Computer

When processing large volumes of data or when large databases must be accessed by many users, a centralized computer is used. Information from a centralized computer is commonly delivered by printed reports or as output on a CRT terminal.

When a centralized computer is to be used for an application, a formal process will usually follow to develop the application system. Management and other personnel who will be using the system will be involved with the professional staff of the information systems department in the design and implementations of the system. This process of design and implementations can be lengthy and difficult.

Once the system is designed, it can be used by all personnel who are authorized to use it. In some applications, such as airline reservation systems a centralized computer will be used because the speed and data access available on a large, powerful computer are required by the application.

For example in a banking application thousands of accounts must be accessible by hundreds of tellers and other bank employees. A large computer is the only machine with the processing power to satisfy the requirements of their applications.

DATA AND INFORMATION

Data:The word data is plural form of DATUM, which means raw fact (i.e.) collection of facts

is said to be data. The data is a name given to basic fact such as names and numbers. Data may be numeric such as date, price, weight, number of items sold, students marks etc., Data may be non-numeric such as customer names, student names, addresses, product names etc.,

Information:The processed data is called INFORMATION (i.e.) when data is connected into

meaningful results it becomes information.

Raw data Processed Information

Difference between Data and Information

Data Information

Raw Fact Finished meaningful one. Unprocessed Processed Unstructured Structured What exists what required.

DATA PROCESSING:

1, 2 1+2 3

Data Processing means conversion of data into meaningful information ie.Data processing means calculating or manipulating data. The mere data cannot solve problems so the data is arranged by the computer to produce meaningful information.

Processor

Processor is a hardware device, which is used to process the data. There are different types of processors namely 80286, 80386, 80486, Pentium series etc.

Data Processing Cycle:

(1) Preparation of source documents.(2) Input of data(3) Manipulation of data(4) Output of information(5) Storage of data

Source documents:The first step is to obtain the relevant facts and figures and to set these out

on source documents. For example, in a population survey, the name, address, age, sex, occupation, etc., must be first written down onto a survey sheet or some other document. These documents may be so designed that information is recorded in the same structure as the data required by the computer program.

Input:Once the data has been extracted from the source document, it must be

supplied to the computer through input devices like keyboard etc.,

Data Manipulation:This includes all the operation performed on the raw data. It can do arithmetic

operations like addition, subtraction, multiplication and division on the data. It can compare the data whether it is greater than or less than or equal to by using relational operator (<,>, =). It can also carry out logical operations by using (and, or, not).

For example, in the population survey, we may want to classify people by occupation or age.

Storage Device

Source documents

Input

Processing

Output

Output of Information:The objective of outputting results is to provide meaningful information to

managers, accountants, population survey analysts etc.Careful consideration should be given to the presentation of results so that they can

be digested easily and quickly.

Data Storage:

In most cases, the results of processing one set of data are retained for future use or reference. This means data processing installations require a great deal of secondary storage space to store all the programs and the different sets of data.

Types of Data Processing:

Manual Data Processing Mechanical Data Processing Electronic Data Processing

Manual Data Processing:

In manual data processing human being converts the data into information. Mere data is processed using manual operations.

Mechanical Data Processing:

In mechanical data processing, a person uses various machines to get the work done. E.g.: calculators, tabulators etc. This method has both human interaction and machine operation.

Electronic Data Processing:In electronic data processing the data is processed by the computer.

DATA STORAGE:Retaining data for future reference is said to be data storage. The data and

instruction that are entered into the computer system through input units have to be stored inside the computer before the actual processing starts. The results produced by the computer after processing must also be kept inside the computer before passing to the output units. The intermediate results are also stored inside the computer.

Thus the functions of storage units are to hold

All the data to be processed. Intermediate results. Final results after processing.

The data stored in a location called memory referred by its address. There are two classes of memory called main memory and secondary memory. When the data is stored outside the processing unit it is called as external storage or secondary storage or auxiliary storage.

Example: hard disk, magnetic tape, magnetic disk, floppy disk etc.The secondary storage is needed because the size of the main memory is limited. When the data is stored inside the processing unit , it is called as internal storage or main memory or primary memory.Example: RAM

Difference between main memory and secondary memory

Main memory Secondary memory

Data cannot be kept for long time. Data can be kept for long time Memory size is small. Memory size is large Expensive Not expensive An integral part of the computer. Not an integral part of the system Not transportable Transportable

Types of Main Memory:

RAM(Random Access Memory) ROM(Read Only Memory)

RAM:Random Access Memory is also called as Read/Write memory. The main memory of

the computer is made up of RAM chip. Data can be written into a RAM chip and be read. It can also be erased and re-written. When the power is off any information stored in the memory is lost.

ROM:Information can be written into ROM chip only once. Once written, it cannot be

altered and no fresh information can be written into the memory. When the power is off the data stored inside the ROM will not be lost.ROM can be classified into:

PROM(Programmable Read Only Memory) EPROM(Erasable Programmable Read Only Memory)

PROM:The ROM chips are supplied by the computer manufacturer while purchasing the

computer system. It is not possible for a computer user to modify the program stored inside the ROM chips. But it is possible for the user to store his own program in PROM chip. Again once it is programmed, recorded information cannot be changed.

EPROM:Once the information is stored in ROM and PROM, it cannot be altered or changed. To

remove this problem EPROM was introduced. It is possible to erase the program inside the chip using ultra-violet rays.

Difference between RAM and ROM:

RAM ROM

The information is stored and retrieved Constructed by the by the programmer’s choice manufacturer. Information stored

in this memory cannot be modified by the programmer

Volatile memory (ie.Information will Non – Volatile memory.be lost on power failure)

Used to store programs in execution. Permanent functions like Sinx, cosx are stored.

Easiest to change ROM’s are expensive to Change.

DATA RETRIEVAL:

Recovering or getting back stored data is called the data retrieval. Data retrieving is a process of searching or locating a data item from the storage. The data can be retrieved from the storage device in sequential mode, indexed mode, and random mode.

Sequential Storage and Retrieval:

Each record is stored on the tape or disk one after another and the data is retrieved in the same sequence as they are stored. For example: the file having student details, records are stored in sequence by social security number. The data in the file is retrieved one record after another and processed in the same sequence as it is stored in the file. In most cases, when sequential retrieval is used, the data is stored in some defined sequence based upon a value in record (called a key), such as social security number in this example.

Disadvantage:

Sequential retrieval has a major disadvantage – since records are retrieved one after another in the same sequence as they are stored, the only way to retrieve the third record is to read the two preceding records first. Because of this, sequential retrieval is never used when fast access to a record is required. Instead, sequential retrieval is used when records are processed one after another, such as when creating printed reports.

Random or Direct Access Retrieval:

Data stored on magnetic disk can be randomly retrieved, which means records can be retrieved regardless of the order in which they are physically stored. Random retrieval can be used when fast access to a record is required.

In most cases, records are randomly retrieved based upon a value within the record itself. To illustrate this, sample records containing an account number, customer name, and the account balance are stored on disk. When a customer with account number 124 wants to know his balance, the application requires that the program be able to immediately retrieve the data. Sequential retrieval would not work here.

A request is made to the system for the balance in account number 124. The record associated with the account number will be directly retrieved and brought into main memory. From there the program can display the balance on the CRT screen. This ability to randomly access records based upon a value in the record is very important. In this example the record is accessed based upon the account number stored in the world.

Indexed Mode Retrieval:

The indexed mode combines both sequential and random mode of processing. For example: A file has 2000 records, in that file 1220 to 1250 records have to be retrieved. The computer will locate the record number 1220 randomly and access the records up to 1250 sequentially. The online data storage and retrieval is very useful for the functioning of modern business. The online device means those devices that are directly connected to the CPU.

COMPUTER APPLICATIONS IN VARIOUS AREAS OF BUSINESS

In the computer-related industry, numerous career opportunities in a wide variety of areas are available. In Information systems departments, opportunities can range from such diverse jobs as data entry operators to business or scientific programmers. Those with an entrepreneurial flare will find opportunities in S/W development, consulting and education. Many opportunities exist in both small and large companies for those interested in pursuing a career in the information processing industry.

Computer Operations Personnel: Computer operations personnel are those who are responsible for the day-to-day operations.

Computer Operations Manager: The Computer operations manager is in-charge of the entire operations such as, responsible for hiring and assigning the other operations personnel, establishing operations center policies, planning the installation and removal of equipments and generally doing all other activities to ensure the processed data is efficient.

Computer Operators: Computer operators are the people running the equipment in the computer center. Their job includes loading tapes and disks, monitoring system performance and initiating solutions to malfunctions.

Data-Entry operators: Data entry personnel are the people who enter data into the computer systems.

System Librarians: System librarians are responsible for data stored offline such as on tapes and disks, and to back-up copies of important programs and data for future references.

System Analyst: Systems analyst is responsible for analyzing, designing and implementing large computer based information systems. Since they are the interface among users, upper management and programmers, they must be skilled in business, computer technology, interpersonal communications and people.

Programmers: Computer professionals who specifically write computer programs are called as programmers. They are classified as application programmers, maintenance programmers and system programmers.

Application programmers write application programs i.e., S/W that serves the direct needs of end-users.Maintenance programmers maintain and update application programs, and keep application programs running for years after they were written.System Programmers write system S/W that control the operation of computer H/W and make it possible to run application programs.

Information Center Personnel: Information center is meant to help endUsers choose the decision support resources they need in order to perform better, training users to use specific S/W package and to set standards for the growth of personnel computing resources within the firm are some of the other functions performed by information center personnel.

Management Information Systems Management (MIS):They are responsible for full range of MIS related activities such as transaction processing , telecommunications, data administration and ebd-user support.In many organizations a ‘data processing director’ is responsible for all personnel involved with the company’s major transaction processing applications.

Database Administrator: They are usually responsible for ensuring both the integrity and security of the data in the database.

Telecommunications Managers and Network Managers are responsible for meeting the data communication needs of users in the organization.

Hardware Industry

Today the hardware portion of the information processing industry includes personal computer manufacturers, small business computer manufacturers, mini computer and mainframe manufacturers, and manufacturers of peripheral devices including computer terminals, disk drivers and printers. Data communication equipment, office automation equipment, and computer assisted manufacturing hardware are an important part of the information processing industry.

Additional jobs may be found working for computer manufacturers, s/w companies, service and supplies companies, and retail computer h/w and s/w stores etc. These jobs include Sales Representatives after comprehensive training by the company; call upon the prospective customers with the intent of selling them the hardware. Systems engineer is a term used by some companies to describe individuals echo are technical specialists and serve as consultants to customers.

COMPUTER RELATED JOBS IN BUSINESS

Payroll and personnel records

Office Automation

Word processing

Desktop publishing

Electronic office

Stock control and sales

Banking

Insurance and stock broking

UNIT-2

Introduction about computer systems:

Our society is being reshaped by rapid advances in information technologies, Computer, Telecommunication networks and other digital systems that have vastly increased our capacity to know, achieve and collaborate. These technologies allow people to transmit information quickly and widely, linking distance places and to create communities that just a decade ago were unimaginable.

It is difficult to appreciate just how quickly information technology is evolving. Five decades ago ENIAC, one of the earliest computers stood ten feet tall and stretched eighty feed wide; while today, one can buy a musical greeting card with a silicon chip that is 100 times faster than ENIAC. This extraordinary phase of information technology is bringing people and cultures together and creating new social dynamics in the process.

It is leading to the formation of closely bonded and widely dispersed community of people united by their interest in doing business orin sharing experiences and intellectual pursuits. New forms of knowledge accumulation are developing, as are computer based learning system that opened the way to innovate modes of instruction and learning.

A computer is an electronic machine, operating under the control instructions stored inside its memory. As an aid in problem solving, it accepts data, both numeric and

non numeric, processes and presents it in the desired form.The following are the various types of computer systems:

VARIOUS TYPES OF COMPUTER SYSTEMS

1. Analog Computers

Analog is the Greek word, which means similar. So, in analog computers, the similarities between any two quantities are measure by electrical voltages or current. The analog computers operate by measuring instead of counting.The analog computer works on the supply of continuous electrical signals. The display is also continuous. Its output is in the form of graphs.

Analog Signal: An analog signal is a continuous variable electromagnetic wave. It can consume an infinite number of voltage or current values.

Characteristics of analog computerThe analog computer has the following important characteristics:a) It operates by measuring.b) It requires physical analog.c) It functions on continuously varying quantities.d) The output is usually represented in the form of graph.e) In analog, the calculations are first converted in equation and later converted into electrical signals.f) The accuracy of the output is poor.g) It has limited memory space.h) It is not versatile. i.e., it has limited application.i) The speed of analog computer is low.j) Not suitable for business and industry.

2. Digital Computers

These computers work with quantities represented as digits. They operate on discrete quantities. In digital computer, both numeric and non-numeric information are represented as strings of digits. These computers use binary codes, 0’s and 1’s, to represent the information.

The information is given to the computer in the form of discrete electrical signals. The basic operation performed by a digital computer is addition. Hence, the other operations such as multiplication, division, subtraction and exponentiation are first converted into “addition” and then computed.

Characteristics of digital computerThe digital computer has the following characteristics:a) It operates by counting.b) It functions on discrete numbers.c) The calculations are converted into binary numbers i.e., 1s and 0s.d) The output is represented in the form of discrete values.e) Its accuracy is good.f) It has large memory spaceg) It is versatile in nature and is suitable for a number of applicationsh) In digital computers, the numbers, words and symbols can be used.i) Its processing speed is high.j) It is highly suitable for business application.

3. Hybrid computers:

The computer which possess the features of both analog and digital computers are called hybrid computers. That is, the hybrid computers have the good qualities of both analog and digital computer.

With the hybrid computer the user can process both continuous and discrete data. This computer accepts either digital or analog or both types of input and gives the results as per requirements through special devices. In the hybrid computers a converter is fixed to convert the analog data into digital data and vice versa. These are special purpose devices and are not widely used.

4. General Purpose Computer

These are designed and constructed to cater almost all the needs of the society. They can perform various operations. In fields of engineering, science, commerce and industry. They are able to perform according to the programs created to meet different needs. The general – purpose computer can be used to prepare stores reports, sales reports, payroll, etc. a general purpose computer can solve a much broader class problems specifically a general purpose digital computer is remarkably versatile.

5. Special Purpose Computers

These computers are designed to solve a particular problem or task, the computers are provided with limited memory and speed necessary for a particular job. The instructions needed to perform the particular task are incorporated into the internal memory of the computer. It does not possess unnecessary options, hence it is economical. E.g. Business purpose computers and scientific purpose computers.

6. Micro Computers

Because of its small size and the use of micro-processor, this computer is called micro computer. All the computers have three units namely input, output and central processing unit, (CPU). The entire CPU is contained in a single or a few microchips. When equipped with memory and input/output control circuitry, it is called micro computer. Its storage capacity is low when compared to mini and main frame computers. It is able to accept most of the high level languages. However, it uses an interpreter or complier for running high level languages.

Microchips contain micro-electronic circuitries which are very tiny. Large numbers of these can be packed tightly on to a single tiny piece of silicon. Silicon is a material found in sand. The microchip is made by building up a series of very thin layers of silicon and of the tiny components which are held in it.

Special purposeThe Micro computers are small and portable. They are relatively inexpensive; the micro computers have excellent graphic capabilities. The maximum word length varies according to the configuration of the microcomputers.

Kinds of MicrochipsThe microchips can be classified as follows:a) Micro Processors: These are the most powerful kind. They are almost tiny computers in themselves. Each one ahs a processing Unit, a memory and a special area to handle input and output. Microprocessors are the most important part of the CPU of a modern computer.

b) Memory Chips: These are the common form of computer memory. They are used to hold information either temporarily or permanently.c) Input and Output Chips: In these chip circuits the flow of information is the both directions.

Features of Micro Computers

a) Its storage capacity is low.b) Its rate of acceptance and transfer of data is limited i.e., a maximum of 5 lack bytes / second.c) It is able to accept most high level languages. However it uses an interpreter when running high level language because most micros do not have sufficiently large memory to support compliers.d) The maximum word length it holds is 16-bits.

Advantages

a) They are small and portable.b) They are relatively inexpensive.c) They work as soon as they are switched on.d) They have excellent graphic capabilities,e) They do not occupy much space.f) They do not consume much power.

Disadvantages

a) Micros have a limited storage capacity.b) They are relatively slow.

7. Workstation

Workstation is a type of computer used for engineering applications (CAD/ CAM), desk top publishing, software development, and other types of applications that required a moderate amount of computing power and relatively high quality graphics capabilities. Workstations generally come with a large, high-resolution graphics screen, at least 64MB (Mega bytes) of RAM, built – in network support, and a graphical user interface. Most workstations also have a mass storage device such as a dish drive, but a special type of workstation, called a diskless workstation, comes without a disk drive.

The most common operating systems for workstations are UNIX and Windows NT. In terms of computing power, workstations lie between personal computers and mini-computers, although the line is fuzzy on both ends high-end personal computers are equivalent to low-end workstations. And high-end workstations are equivalent to minicomputers. Like personal computers, most workstations are single-user computers.

8. Mini Computers

The size of the mini-computer is in between the size of micro and main frame computers. It is more powerful than a micro computer. Mini computers are usually designed to serve multiple users. Today, mini-computers are the popular data processing systems in the field of business and industry. These computers accept all high level languages.

Characteristics

1. It is a general purpose machine with a smaller CPU than a main frame2. Its storage capacity is about 2 mega words3. Its word lengths are usually 12, 16, 24, 32 bits.4. Its rate of acceptance and transfer of data is a maximum of 4 million bytes/seconds5. It can support all high level languages.6. It can support many terminals i.e., more than 20 terminals.

Advantages

a) It performs almost all the tasks that a mainframe computer does.b) It is relatively inexpensive and is within the purchasing power of the small and medium sized business firms.

Disadvantages

a) They are very expensiveb) They required large room space.c) Their consumption of electricity is very high.d) Maintenance coast is also very high.

Main frame computers

These computers are huge and dynamic with action. They occupy a large space. Its transfer rate is very high. The word lengths are higher than the other computers. These computers are able to accept any high level language. A mainframe computer can support more number of terminals. Hence, it is also called as a “central host computer”

Advantages:

1. They are capable of handling all tasks2. The storage capacity is about 10 mega words3. The transfer rate is very high i.e millions of bytes per second4. The word lengths are either 24,32,48,64 or 128 bits.5. They are able to accept any high level language.6. It can support around 500 terminals

Disadvantages:1. They are very expensive2. They require large room space3. Their consumption of electricity is very high4. Maintenance cost is also very high

9. Super Computers

The super computers are very costly. Hence it is rarely used. Its capacity is abnormally high, it cannot be compared with any other computers in capacity, function, speed, accuracy, language etc., they have operations done in parallel, rather than sequential. They are employed for specialized applications that require immense amounts of mathematical calculations.

The chief difference between a super computer and a main frame computer is that a super computer channels all its power into executing a few programs as fast as possible. But

main frame uses its power to execute many programs concurrently. CRAY – 3, Cyber 205, and PARAM are some well known super computers.

Characteristics

a) They use several processors working simultaneously.b) They process at a rapid speed.c) The main memory ranges form 8 to 64 megabytes.d) They have operations done in parallel, rather than sequentially. They are used in weather forecasting, supersonic aircrafts design and other works that require billions of calculations per second.e) They can be used for animated graphics-fluid dynamic calculations etc.,

10. Laptop computer:

Laptop computer, simply laptop (notebook computer or notebook), is a small mobile computer, which usually weighs 2-18 pounds (1-6 kilograms), depending on size, materials, and other factors. Laptops usually run on a single main battery or from an external AC/DC adapter which can charge the battery while also supplying power to the computer itself. Many computers also have a 3 volt cell to run the clock and other processes in the event of a power failure.

As personal computers, laptops are capable of the same tasks as a desktop computer, although they are typically less powerful for the same price. They contain components that are similar to their desktop counterparts and perform the same functions, but are miniaturized and optimized for mobile use and efficient power consumption.

Laptops usually have liquid crystal displays and most of them use different memory modules for their random access memory (RAM), for instance, SO-DIMM in lieu of the larger DIMMs. In addition to a built-in keyboard,they may utilize a touchpad (also known as a track pad) or a pointing stick for input, though an external keyboard or mouse can usually be attached.

INTRODUCTION: GENERATIONS OF COMPUTERS

The history of computer development is often discussed with reference to different Generations of computing devices. In computer terminology, the word generation is described as a stage of technological development or innovation. A major technological development that fundamentally changed the way computers operate resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices characterize each generation of computers.

1. First Generation (1940-1956): Vacuum Tubes

First generation computers were vacuum tube / thermionic valves-based machines. These computers used vacuum tubes for circuitry and magnetic drums for memory. A magnetic drum is a metal cylinder coated with magnetic iron-oxide material on which data and programs can be stored. Input was based on punched cards and paper tape, and output was displayed on printouts.

First generation computers relied on binary-coded language (language of 0s and 1s) to perform operations and were able to solve only one problem at a time. Each machine was fed with different binary codes and hence were difficult to program. This resulted in lack of versatility and speed. In addition, to run on different types of computers, instructions must be rewritten or recompiled.

Examples: ENIAC, EDVAC, and UNIVAC.

Characteristics of first generations computers:

These computers were based on vacuum tube technology. These were the fastest computing devices of their times. (Computation time was in milliseconds) These computers were very large, and required a lot of space for installation. Since thousands of vacuum tubes were used, they generated a large amount of heat.

These were non-portable and very slow equipments. The lacked in versatility and speed. They were very expensive to operate and used a large amount of electricity.

These machines were unreliable and prone to frequent hardware failures. Hence, constant maintenance was required. Since machine language was used, these computers were difficult to program and use. Each individual component had to be assembled manually. Hence, commercial appeal of these computers was poor.

2. Second Generation Computers (1956-1963): Transistors

In the sixties, there was lot of development in semiconductor field - a field of materials. In vacuum tubes, a filament is heated to emit electrons,(the basic component of an atom)that carry current. In 1946,Willam Shockley and a few of his colleagues invented transistors, which do not need any heating to liberate electrons in addition to being smaller in size, they saved power due to the absence of heating and hence the cooling needed.

The smaller size resulted in smaller distances that the electrons have to travel to transmit information from one part of the computer to another. Hence calculations became faster. The reliability also increased. Today you cannot see any second generation computers. The smaller size of components saw mass production of computers which became cheaper.

Many companies started buying and using them increasing the demand. Computer programming languages developed further to make programming easier and user friendly. Yet if you compare today’s computers, they were a lot behind. The increased use of computers and the consequent mass production sent the prices crashing down. Computer scientists and electronic engineers were developing more sophisticated computers.

Characteristics of second generation computers:

These machines were based on transistor technology. These were smaller as compared to the first generation computers. The computational time of these computers was reduced to microseconds form milliseconds. These were more reliable and less prone to hardware failure. Hence, such computers required less frequent maintenance.

These were more portable and generated less amount of heat. Assemble language was used to program computers. Hence, programming became more time efficient and less cumbersome. Second generation computers still required air conditioning. Manual assembly of individual components into a functioning unit was still required.

3. Third Generation Computers (1964 - early 1970s): Integrated circuits

In second generation computers, one could recognize the circuit components such as transistors, resistors and capacitors distinctly. There were physically separate or “discreet”. Slowly scientists started integrating these components together so that they are not separate. They were fused into the circuits. People called it large scale integrated circuits (LSI).

Computers using such components were called third generation computers. Since components were packed together more densely, the size of computers became smaller. Programmers also developed more sophisticated software. By 1970, engineers developed a device called microprocessor. Lot of circuits was packed into it. Intel 4004 was one such chip.

Characteristics of third generation’s computers:

These computers were based on integrated circuit (IC) technology. They were able to reduce computational time from microseconds to nanoseconds. They were easily portable and more reliable than the second generation. These devices consumed less power and generated less heat. In some cases, air conditioning Was still required. The size of these computers was smaller as compared to previous computers. Since hardware rarely failed, the maintenance cost was quite low.

Extensive use of high-level languages became possible. Manual assembling of individual components was not required, so it reduced the large requirement of labour and cost. However, highly sophisticated technologies were requiredfor the manufacture of IC chips. Commercial production became easier and cheaper.

4. Fourth Generation Computers (Early 1970s – till date): Micro processors

More and more circuits were packed in a microprocessor. The components were integrated further and very large scale integration (VLSI) technology revolutionized computer field further. Intel Corporation made chips such as 8080 and 8086 to be followed by 80286, 80386, 80486 and now the Pentium processor. These chips perform calculations faster.

They are not only used in computers, but also in measuring devices and even in house hold devices such as washing machines. Computers using such VLSI chips progressively shrunk in size. Computers using the microprocessors are termed as microcomputers. The software technology also developed further. Programmers developed more sophisticated and user friendly software. In course of time, the cost of these computers have come down so much that even individuals bought them so they came to be known as personal computers.

Characteristics of Fourth generation computers:

Fourth generation computers are microprocessor-based systems.These computers are very small. Fourth generation computers are the cheapest among all the other generations. They are portable and quite reliable.These machines generate negligible amount of heat, hence they do not require airConditioning.

Hardware failure is negligible so minimum maintenance is required.The production cost is very low. GUI and pointing devices enable users to learn to use the computer quickly. Interconnection of computers leads to better communication and resource sharing.

5. Fifth Generation Computers (Present and beyond): Artificial IntelligenceUp to fourth generation, the classification was based purely on hardware. Fifth generation computers are classified based on software also. VLSI technology is used in fifth generation computers. They have large main memories. The speed is also high. In addition to all this, Fifth generation computers run software called ‘expert systems’.

Characteristics of Fifth Generation computers:

Mega Chips:

Fifth generation computers will use super large Scale integrated (SLSI) chips, which will result in the production of microprocessor having millions of electronic components on a single chip. In order to store instructions and information, fifth generation computers require a great amount of storage capacity. Mega chips may enable the computer to approximate the memory capacity of the human mind.

Parallel Processing:Most computers today access and execute only one instruction at a time. This is

called serial processing. However, a computer using parallel processing accesses several instructions at once and works on them at the same time through use of multiple central processing units.

Artificial Intelligence (AI):

It refers to a series of related technologies that tries to simulate and reproduce human behavior, including thinking, speaking and reasoning. AI comprises a group of related technologies: expert systems (ES), natural language processing (NLP), speech recognition, vision recognition, and robotics.

DATA PROCESSING SYSTEMS

INTRODUCTION

The methods of data processing depend upon the following factors:(a) Volume of data to be processed(b) Complexity of data processing operations(c) Computational demands(d) Processing time constraints and(e) Economic factors.Various methods or modes of data processing are given below:

(i). the single user system(ii). Batch processing(iii). Multi-programming(iv). On-line Processing(v). Real-Time processing(vi). Time sharing concept(vii). Distributed processing

8.2 DATA PROCESSING SYSTEMSThe methods of data processing are explained below:1. The single user system

It is one-man show and is indicative of one of the earlier stages of computerDevelopment. Here only one person can work at a time. Hence, especially if the machine is meant for the use of many persons, much computer time is wasted waiting for one person to finish and debug his program on the machine.

2. Batch Processing

This is an old system but even today it is used for data processing in computing machines, in which the capacity of the CPU is limited. In this system, the data is collected for a predetermined period of time, after which it is accumulated in sequential manner. In this system the source transaction documents are first collected before being sent to computer room. A batch of transactions is entered onto a computer media by data entry devices.

The transactions are validated during data entry and verified with the source documents from the check lists. The validated and verified results on reports are returned to the user departments. In batch processing system the emphases is on maximizing the computer resource utilization. In batch processing, the processing cycle called Batch processing cycle repeats itself at every regular interval. The elements this cycle are given below:

(i) Data capture.(ii) Data transmission.(iii) Data transcription, verification and validation.(iv) Job Processing.(v) Job assembly putting together the batch for processing.(vi) Job disassembly (separating out the reports after processing)(vii) Reports and distribution.

Features

(a) Here, the data is accumulated into batches and processed periodically.(b) The jobs are processed one after the other without any user interaction.The concept of Batch Processing is dearly explained with the help of the followingdiagram:

Examples of applications which can use batch processing are:

(1) Payroll Processing: In payroll processing the data are collected for a stipulated period of time usually one month and processed at regular intervals after which payments are distributed to all the employees.

(2) Telephone Billing: Here the subscriber does not get a bill for every call he makes. Instead, his calls are recorded at a centralized place and are processed on a predetermined period of time to prepare his bills.

(3) Financial accessing

(4) Budgeting and budgeting control

(5) Production planning and control

(6) Project planning and control

(7) Project planning and control

Drawbacks in Batch Processing:

The following are the drawbacks of batch processing:1. Time gap between capture of data2. Time consuming to debug3. Delay in generating reports

3. Multi-programming:

In batch processing, programs are executed one by one. The memory and ALU of the machine are not being fully utilized. To get the maximum use of the machine, multiprogramming system is used. “Multi-programming enables to store and execute more than one program in the CPU at the same time”. The multi-programming concept is event based. The purpose of multi-programming is to increase utilization of the computer system as whole.

Multi-programming is defined as execution of two or more program that all reside in primary storage. Since the CPU can execute only one instruction at a time, cannot simultaneously execute instructions from two or more program. However, it can execute instructions from one program then from second program then from first again, and so on. This type of processing is referred to as concurrent execution. Using concept of concurrent execution, multi-programming operate in the following way:When processing is interrupted on our program, perhaps to attend an input or output transfer, the processor switches to another program.

This enables all, parts of the system, the processor, input and output peripherals to be operated concurrently thereby utilizing the whole system more fully. When operating on one program at a time the processor or peripherals would be idle for a large proportion, if the total processing time, even though this would be reduced tosome extent by buffering. Buffering enables the processor to execute another instruction while input or output is taking place rather than being idle while transfer was completed. Even then, when one program is being executed at a time, basic input and output peripherals such as floppy Reports disk drive and line printers are slow compared with the electronic speed of the processor and this causes an imbalance in the system as a whole.

However, in a multi-programming environment the CPU can execute one program's instructions while a second program is waiting for I/O operations to take place. In a system of multi-programming storage is allocated for each program. The areas of primary storage allocated for individual programs are called ‘partitions’. Each partitions must have some form of storage protection and priority protection to ensure that a program must have some form of storage protection to ensure that a program is one portion will not accidentally write over and destroy the instructions of another partition and priority (when two or more programs are residing in primary storage) because both programs will need access to the CPU's facilities (e.g.; the arithmetic and logic section)

A system of priority a method that will determine which program will have first call on the computer's facilities is normally determined by locating the program in specific partitions. Programs that have the highest priority normally are stored in an area called the ‘foreground partition’. Programmers’ with lowest priority are stored in an area called ‘background partition’.

4. On-Line Processing

Definition of Online Processing:

Online processing refers to processing of individual transactions as they occur from their point of origin as opposed to accumulating them into batches. This is made possible by such direct access devices as Magnetic disk and Magnetic Drum and number of terminals connected to, and controlled by a central processor. In this way, various departments in a company can be connected to the process by cables. If operating companies are a number of miles away from the processor then they are linked by means of telegraph or telephone lines.

This type of processing provides multi access to information files by terminal users and also enables them to update with transactions data. It is a non-sequential process in which data is directly transmitted between input/ output device and a computer system via communication links. It is a method of processing where many users have direct access to the same system, and where the file is updated as soon as the transaction is completed.

Special Features

1. In this method data is not accumulated, instead it is entered and executed directly.2. Quick Processing - By means of direct communication with the computer and continuous flow of input, the delay between transactions and their processing is avoided.3. This method reduces the data entry errors, because the user who generates, the data is the one who keys it in.4. This system validates data at various points and ensures that correct data is being entered.5. Under this method the system performs the whole task in a conversational 'manner helping the data entry process.6. In on line processing, one has the latest update immediately.

Online processing ensures that the records are in updated at any time whereas this is so with batch processing say once a week but the fact remains that online processing is usually more costly. Therefore in choosing one of the processing both updating of records and costs are to be considered.

CONCEPT OF ON-LINE PROCESSING

On-line Applications:Systems are being developed and are already in use for a wide range of application

indifferent type of industries described below:a. Electricity and Gas Boards: By means of terminals situated in showroom it is possible to inform perspective customers of the availability of the appliances in response to their inquiries.

b. Banking: It is possible to inform bank customers of the status of their accounts in response to an inquiry by accessing relevant file using on online terminal.

c. Tour Operators Reservation Offices accept telephone inquiries from travel agentsregarding the availability of holidays in respect of client's inquiries. By means ofterminals, the availability of the required holidays can be checked and booked

immediately.

d. Stock Exchange: Terminals located in major stock Exchange through out the country and the offices of participating brokerage from enable the speedy processing of share dealings.

e. Stock Control: Terminals located in warehouse provide the means for automaticrecording of stocks, updating of stock records, reservations, follow-up of outstanding orders and the printing of picking list etc., Benefits provided by Online Systems: Online systems provide a number of benefits all of which assist in improving administrative efficiency which is essential in today's competitiveBusiness environment. A number of benefits are out-lined below:

a. Integration of clerical work with the computer:On-line systems assist in harnessing activities of clerical staff to the computer by the use of terminals. They can have access to information which they require for the efficient performance of their jobs in dealing with customer enquiries and order processing.

b. Elimination of tedious tasks:Routine clerical tasks are replaced by terminal operations providing a greater degree of job interest, operating efficiency and job satisfaction.

c. Reduction in paper work:Volume of paper work generated by normal clerical system and batch processing system is relatively high. Online systems reduce the volume of print out required for management report since the information can be displayed on terminal screen on demand.

d. Improved accuracy:As terminal messages are checked accuracy before being transmitted to the computer by data validation programs, the quality of formation in a system increases as the input errors are reduced. Hence, information is more reliable.e. File updating improved:Master files are more easily updated by terminal key board with regard to transaction data, as special runs do not require to be set up as is the case with batch processing applications.

f. Management Information more readily available:Management information becomes more readily available by direct access facilitieswhich enables mangers to obtain a greater degree of control to the operations for which they are responsible.

g. Improved customer services:Improvements in the level of customer’s service can be expected in these systemsConcerned with appliances sales, booking systems and accounting enquiries.

h. Reduced data preparations cost:On-line system dispense with the need to convert human sensible data into machine sensible data thereby eliminating punching and verifying operations. This saves time and the cost associated with such operations.

5. Real Time ProcessingIt is also called as interactive mode or Direct mode. This system makes the user to

have direct contact with the computer through his terminal. It is an alternative approach to an on-line processing system. Here the data is processed, the instant it occurs. There is no delay between the time data is available, and the time it is processed.

The term real time refers to the technique of updating files transactions date immediately after the event to which it relates occurs. This is in distinction to batch

processing which processes related data to batches of pre-defined periods of time. Real time systems are basically on-line systems with one specially in inquiry processing. The response of the system to the inquiry itself is used to control the activity. An on-line production data collection system that simply accepts input and utilities it for payroll and costing purposes cannot be termed real-time,but if, on the other hand, the system is designed to provide immediate information to monitor the production processes, it is a real time system.

Special Features(a) Program is always under execution.

(b) It produces output to control, direct or affect the outcome of an ongoing activity or process.(c) In this method, the control is exercise during the actual functioning.(d) It is meant exclusively to perform one task.(e) It is like an online system with; title constraints on response time availability.(f) It is called a real time system because it has to give results based on deadlines which are imposed by the real world outside.(g) The data which has to be produced by the systems has to be in such a less time, that they can influence the external events which are based on this data.

Thus the response of a real time system is one type of feedback control system. The response time would naturally differ from one activity to another. If the example, it is the launching of a space vehicle, the response time should be in split second whereas in business situation even a few minutes of response time may be alright.

Online updating in real time usually leads to transaction as a by-product. For example, the updating in real time a customer's order may lead to such transactions as dispatch noted and purchase requests, etc. Real time systems offer accountants and others in business a chance to fulfill the potential of the computeras a tool of management.

Concept of Real Time Processing

Guided Missile System

Real Time Processing is suitable in the following type of business operations:i. Wholesale supplier and manufacture - Availability of stocks.j. Airline - Flight seat availability.k. Manufacturing - Status of production orders.l. Process Control.m. Space Craft Control.

Real time systems usually operate in multi-programming and multi-processing: This increases both availability and reliability of the system. CPU's in real time system should possess the, capability of what is known as program interrupts. These are temporarily stoppage or halts in the execution of a program so that more urgent messages can be handled on priority. It may be worth noting that some computers systems are dedicated to real time operations and others are

Terminal 1Terminal 2Terminal 3Terminal 4

Computer Data designed to operate in both batch and real time modes so that they can also serve as stand by unit to each other.

6. Time Sharing

It is a special type of on-line processing in which several users share the resources of an on-line computer system to avoid turn about time, especially when results are needed quickly; another system is available i.e., time sharing system. In this method the individual user has an independent local terminal. The terminal is connected to a main computer, which does all the processing work.

Under this system each person on a terminal has to log into the system. The system then lists him in the order in which he has logged on. Once everybody has logged on, the system will permit the first in the list to run his program. The time given for running the program is generally 10 milliseconds. It is called a time slice or a time slot or a quantum.

Starting then, with the first to log on, each user is given his time slice. Once all have made use of it, the system starts all over again, repeating the cycle. The system maintained is called a polling system whereby each terminal is polled on a round robin basis.

All the instructions given by the users are carried to the centrally located main computer system and processed there and retrieve back by the user instantaneously. Since, the centrally located main computer has high-speed processor, users may feel that they are sharing the same computer resources.

Features1. The processor time is shared between two or more persons.2. The processor switches from one user's job to another at a rapid rate under the control of a monitor program.3. This concept is time based..

Advantages of Time-Sharing System

(1) Simultaneously several users can be served.(2) All the users have the same priority.(3) All the users get equal amount of processor time.(4) The interaction with the running programs is possible.

Time-Sharing Vs Multi-programming

The difference between these two methods is that in "time, sharing" the CPU links only one terminal at a time and its total time is shared uniformly by all the users. But in multiprogramming, the CPU links more than one terminal or other peripherals at a time. Therefore, multiprogramming more efficiently utilizes the main memory and the central resources than time sharing. Time sharing is employed only for multi terminal system whereas multi programming is meant both for single as well as the multi terminal system.

7. Distributed ProcessingIn computer science, a form of information processing in which work is performed by

separate computers that are linked through a communications network. Distributed processing is usually categorized as either plain distributed processing or true distributed processing. Plain distributed processing shares the workload among computers that can communicate with one another.

True distributed processing has separate computers perform different tasks in such a way that their combined work can contribute to a larger goal, such as the transfer of funds from one bank to another. This latter type of processing requires a highly structured environment that allows hardware and software to communicate, share resources, and exchange information freely.

At the highest (and most visible) levels, such distributed processing can also require data transfer mechanisms that are relatively invisible to users but that enable different programs to use and share one another's data.

Distributed data processing system is a network of several computers in remote stations, each of which is linked to a single host computer. The larger, central computer maintains the firm's master data base and system log. Each remote system is a fully independent computer that maintains its own local data base in addition to communication with the master computer. These individual computers are tied together through a high speed communication network. This allows individual computers to communicate with one another in a variety of ways depending on the CIS requirements.

Many small computers (called nodes) are employed as data collection points in several departments. They are connected to a main computer system (called File Server) in a centralized department, which controls the entire database. The processing involved here is known as distributed processing.The distributed data processing system exists because of the need for large interactive installations with a high degree of reliability and accuracy. Moreover, large number of mini computers can be connected in this system which results in cost reduction.

Features(a) Decentralized computer system(b) Interconnected by communication network (c) More reliable(d) Since more than one computer is used in the network, it is economical.

Advantages:

Distributed data processing system has many advantages:

a. Local computers on the network offer immediate response to local needs.b. Systems can be expanded in modular fashion as needed because many smallc. Computers are used as the system is not dependant on large unit that could shut down the network if it failed.d. Equipment operating and managing costs are often lower.e. Minicomputers tend to be less complex than large systems; therefore, the system is more useful to local users.

Distributed data processing system a number of computer systems are linked together. So the facilities available-in one computer system can be shared by all. This link is called computer network.

NETWORKING

INTRODUCTIONWith standardized hardware and software, the microcomputers provide user-friendly

environment. It meets the computing requirements of most users. But, the need for z interaction with other computer users and with other computer systems for exchange of data etc., has increased over the years. Networks are increasingly meeting this need. From the users’ point of view the networks may be of two types;

Local area network and Wide area network.

Computer networking is the process of inter connecting two or more computers so that the users can communicate with each other, share resources and overcome other limitations of stand-alone systems. The network can be established with a variety of combinations of computers such as a net of only microcomputers, microcomputers and one or more minicomputers and a set of microcomputers connected to a mainframe computer. The computers in typical network are autonomous in the sense that they have processing capability independentof the network.

ADVANTAGES OF NETWORKING

The main advantages of networking are:

(i). Hardware resource sharing:

Network enables sharing of expensive resources such as processor, storage space and peripherals like modern, fax, and laser printer.

(ii). Sharing of databases:The network permits concurrent access to the same data file by many users in thenetwork. Thus, user in the sales department, production department, inventory department etc share corporate databases.

(iii). Sharing of Software:Any user in a network can load and use the software installed on any of the computer of fileserver in the network.

(iv). Communication between users:The Network users can communicate between them. E-mail facility can also be used for communication.

(v). Decentralized data processing:

In a network, the data processing can be decentralized by enabling local offices to capture and store data, and generate information to meet most of their requirements a local level itself.

(vi) Security of data:

In a networked environment the data is backed up with duplicate storage. Adequatesecurity measures are also put in place to product the data.

TYPES OF NETWORK

The networks can be classified into three; local area network (LAN), metropolitan area network (MAN) and wide area network (WAN). They are explained in the following sections:

1. Wide Area Network (WAN)

WAN is made up of number of autonomous computers distributed over a wide geographical area. WANs were originally developed in the late 1960s to enable communication between computer centers and sharing of hardware, software and other communication facilities. WAN can be implemented using private or public networks. In a

private network an organization takes on lease telephone lines to connect such sites into a network. It is also possible to connect computers in different locations using microwave or satellite transmission.

Public networks are installed by the Government owned telecommunication agencies. WAN spans large geographic distances. It is also called long-haul network. WAN is usually operated at lower speeds then MAN and involves delay.

Most organizations use private networks for communication. Society for WorldwideInter bank Financial Transactions (SWIFT), a non-profit organization of banks, owns a private network. The network exchanges financial transactions between the participating financial institutions, about 3000 in number in over 60 countries.

The terminals of these participating banks are hooked with SWIFT’s access centers. The network offers data communication service 24 hours a day, 7 days a week. INDONET, NICNET, SBINET and WELCOMENET are some of the private network in India. CMC’s INDONET offers e-mail service to customers for a fee. NICNET is a network of National Informatics Center that connects all the district headquarters in the country. SBINET is a private network of State Bank of India and connects its branches across the country. WELCOMNET connects the hotels of the Welcome Group.

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: 1. It operates by means of the international telephone network2. Unlike LANs which owned by their users, WANs operate on public and leasedtelephone lines provided by licensed common carriers, or by other means such satellite and microwave, which are regulated by government agencies.3. Data transmission is somewhere slower.4. The WAN compose any of the following system configurations:5. Single nodes6. Clusters7. LANs

Suppose a company has its central headquarters in Coimbatore and the Coimbatore site contains all departments and equipment for product manufacturing prod 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 shipment and inventory and invoice processing.

Advantages of WAN

The integration of the local nodes into the distributed database linked by the WANprovides the following advantages:1. The WAN allows access to database at remote sites, enabling exchange of data.2. If a remote node fails, remaining nodes on the network can still exchange data.3. If the network fails, the local mode can still access its own database.4. The data used on daily basis by the sales offices resides at the local site, making it easier to retrieve quickly.

5. The local offices can maintain the data more effectively. The corporate office can access the data as needed.6. As a site's database grows larger, its system's storage capacity can be easily upgraded without affecting the transfer of data between other nodes on network.

One of the most significant aspects of a wide area network when comparing it with freedom of a local area network is the involvement of a public telecommunications authority. Regardless of whether the network is made up from system, the controlling authority is almost always the public authority.

In order to protect their equipment and employees, the authority lays down rules, which must be observed by anyone connecting to their lines. In most countries stringent requirements are also imposed on the characteristics of the data transmissions.

2. Metropolitan Area Network (MAN)

Metropolitan area network covers a wider area than a local area network. Usually MAN covers a large metropolitan city and is a scaled down version of wide area network. It operates at high speeds over distances sufficient for a metropolitan area.

3. Local Area Network (LAN)

A LAN is a system of interconnected microcomputers, sharing common resources like disks, printers etc., and links a number of computers workstations) together to allow many people to use the same software and data files. Each user in such a multi-user environment accesses the resources through his microcomputer workstation. The network operating system integrates all the network components and makes operation smooth and transparent.

LAN works in restricted geographical area such as within a large building or offices within a few kilometers. The LAN is an interconnection of computers that need to communicate with each other in a limited geographical area. The network may have other sharable devices attached such as fax, laser printers and copiers. The network includes a central facility with huge storage capacity for the requirements of the organization. It also has a network operating system for managing the network.

Types of LAN:

Local area networks are mainly of two types: Client/ Server LAN and Peer-to-Peer LAN. a) Client / Server LAN

Client Server LAN has servers and clients. The server is a computer that manages shared resources: hardware as well as software and data. It is usually a powerful computer with large RAM and secondary storage capacity. The LAN has a number of microcomputers, called clients, the request the server for services. The LAN may have many servers each specializing in one area of service such as file server, printer server, database server etc. A file server stores program and data files. A database server stores data and a printer server controls printers on thelocal area network.

b) Peer-to-Peer LAN:

In a Peer-to-Peer LAN every computer is equal in status and functioning. All thecomputers on the network are capable of communicating independently with any other computer on the network without using a server. Thus, any computer on the network can access data and programs stored on any other computer. The peer-to-peer LAN is less expensive than client/server LAN. But at the same time this LAN may be slower than a client/server LAN.

UNIT-3

Components of Computer System:

CPU

Memory Unit

Control Unit Input Device Output Device

The computer receives input; processes according to a set of precise instructions and then it presents the output. The computer has to store the information first before it can perform any operations .Input is of two types: program and data which are fed through input device. Then they are transferred to memory under the control of the control unit. During program execution, each instruction is retrieved from memory and interpreted. Control Unit informs the ALU to perform the operations on data. The ALU then executes all calculations and comparisons. Results are then passed to memory where they are held in storage temporarily, prior to presentation by the output device.

Input Unit or Input Devices:

Data and the programs are entered into the computer through these devices. The computer accepts the data to be processed and the instructional details required for processing. When the data and instructions are entered into the input unit they are passed to the memory unit of the CPU. Various input devices are available in this regard. Some of the important input devices are given below:

1. Punched Card Reader.2. Electronic Key Board3. Optical Character Reader4. Bar Code Reader5. Light Pen6. Mouse7. Joystick

Punched Cards:

Punched cards are still in use as medium for recording data and instructions in the form of punched holes to denote and then they are sequentially read by the card reader. The card reader sends the data and instructions to the CPU to process them.

The punched cards used for data processing are made generally of 80 columns and 12 rows. Today 96 columns cards are available. In these cards a hole is punched to represent the binary 1. The absence of a hole represents binary 0. If a card is punched wrongly it cannot be corrected, further the punched cards are not reusable, i.e., cannot be used for any other data. Many numbers of cards are required for the computer programs. Such a collection of card is called a deck. Each card has the left top corner cut to identify the arrangement of the cards is correct or not. The cards are read by a unit called card reader.

Advantages:1. It is very easy to read data on the cards.2. The cards are less expensive than other storage media.3. It is much simple to operate

ALU

4. After inserting a card, if an error is detected the whole system stops functioning.

Disadvantages:1. Punched cards are bulky when put together, so they require large space to store them.1. The cards are easily damaged and perishable2. Transfer of data is relatively very slow3. An on correctly punched card cannot be corrected, it must be replaced.

Optical Character Reader (OCR)An OCR recognizes or interprets printed or handwritten data directly from

documents. The essence of OCR is pattern recognition, i.e. ability to identify a recorded symbol as a familiar from. OCR devices are expensive and are used only where the volume of the data to be fed into the computer is large.

The machine reading is done by light scanning techniques in which each character is illuminated by a light source and the reflected image of the character is analyzed in term of the light-dark pattern produced. Advantages of OCR:i) OCR eliminates the human effort of transcription.ii) Paper work explosion can be handled because OCR is economical for a high rate of input.iii) Since documents have only to be typed or handwritten, not very skilled staff (like the keypunch operators) is required.iv) Further more, these input preparation devices (typewriters etc.) are much cheaper than the keypunch or the key-to-tape devices.

BAR CODE Reader:

Certain data like the product codes of books can be recorded by using printed ‘bar codes’ i.e., alternating lines and spaces which represent data in binary form. As the item having the code is passed over the bar code reader, the reader automatically decides the strips and passes the data to the computer. The typical example of the barcode can be seen on the back cover of books. Normally a barcode has on it number code for the country of the goods origin, the manufacturer and also the item number of that particular product.

KEYBOARD:

The keyboard is the most commonly used and most versatile of all input devices, the keyboard layout is similar to that of typewriters’ with some additional keys. A keyboard may have 83, 84 or 104 keys. Whenever a key is pressed the electrical contacts and circuits just below the key translate the message from the key into equivalent binary codes.

The keyboard is divided into three parts-The main keyboard, the function key and the numeric keypad. Function keys perform some special functions such as loading programs and offering help. These are programmable (i.e., they can be usually made to perform a different function other than the original).

The numeric keypad is used to enter numeric data or to move the cursor. (The cursor is the blinking indicator which indicates where on screen the character that we type will appear). We can switch between these type uses by toggling the numlock keys. Pressing the same key to choose between two modes is called toggling.

Light Pen:Pencil sized units that can be used to print inward and menu items or create

drawings on the screens. In any desired pattern across the screen, LIGHT PEN automatically creates a phosphorescent line, when the it is activated; a sensor inside detects the scanning beam sweeping across the face of the picture tube. A tiny circuit compares this signal with the scanning process to locate the pen’s position.

Mouse:

A small hand-held unit that controls the location of a cursor on the screen when it is slide over the top of a table or other horizontal surface. Its movements tracked by optical means or by sensing the rotation of a ball protruding form the bottom of the mouse. The mouse communicates with the computer through its electrically conducting “Tail”. Buttons on the top of the mouse add an extra element of control. It enables the user to manipulate a pointer or arrow on the screen. The movement of the mouse enables the user to

1. Point to icons (tiny pictures that identify the processing choices)2. Click on such icons to run those programs3. Choose an item from a list (menus)4. Draw lines or pictures on the screen. But they cannot be used where text has to be

entered.

JOY STICKS and TRACKBALLS:

Joysticks provide an alternative method for feeding the computer visually interesting data. When you move the joystick, a cursor on the screen moves in a corresponding way. A trackball is a plastic sphere mounted in a socket so that it is free to rotate in any direction.

OUTPUT DEVICES:

Video Display Unit:

Video display units are the most common output device used today in direct –access processing applications. The keyboard is used to enter data into the computer, and a cathode ray tube (CRT) like a T.V Screen is used to display the input data as well as the messages and processed output from the computer. The CRT produces a beam of electrons that makes the picture on the screen.

The characters or pictures that are displayed on the screen are built up using a combination of dots called ‘pixels’ (i.e. picture elements). Printer:

The Printer is an output device that is used to print documents on paper. Various kinds of printers are used with PCs. The Dot Matrix Printer (DMP) is the most commonly used printer with PCs because of its low cost and reasonably good speed.

The print head in a DMP contains a few tiny needles. There are 7 or 9 needles in a low quality DMP and up to 24 needles in a high quality DMP. At the time of printing, as the head moves from one end of the paper to the other, these needles are fired selectively to print different characters or graphics. Dot matrix printers usually have a printing speed of 100 to 500 characters per second.

Inkjet/DeskJet printers are also fast becoming a popular choice for use with PCs. These printers offer good print quality and noiseless operation. These are non-impact types of printers that print characters and graphics by spraying very tiny drops of ink directly onto paper. The print quality of these printers is much better as compared to DMPs. The Typical print quality of these printers is from 300 dots per inch (DPI) to 720 DPI. These printers can also print in color.

Laser printers are also being commonly used with high-end PCs. Particularly those used for Desk Top Publishing (DTP). The laser printers provide very high quality printout, typically in the range of 300 DPI to 2400 DPI. The typical printing speed of laser printer is between 3 to 12 pages per minute.

Line printers, drum printers and chain printers are some other types of impact printers. These printers are high-speed printers and chain printers are some other types of impact printers. These used with mini or main frame computers, and are not so popular with PCs.

Each Printer has its own style of loading paper and ribbon/ink cartridge in it. If you face any problem in loading paper or ribbon/ink cartridge, refer to the printer manual or contact your printer supplier/vendor.

STORAGE DEVICES:

Magnetic Tape:

Because of the problems faced in the paper media, magnetic substances have come first among these was the magnetic tape. This is also a sequential media for normally between 1.25-2 cms wide and up to 900 meters long. It is made of plastic with a metallic magnetic oxide coating on one side.

Generally, data is recorded on either a 7 parallel-track-tape or on a 9 parallel-track-tape. Writing on and reading from the tape is done with the assistance of READ/WRITE head. The number of characters per inch length of tape stored is called the ‘density’ of the tape. This varies from 550 to 1600 or even 16 k. the 9 Track tapes have the higher densities. Then comparing with the punched card and punched tape, the magnetic tape has certain advantages and disadvantages.

Advantages:

1. Data are stored very compactly.2. It is very easy to handle the Magnetic Tape than the Deck of Cards.3. The Magnetic tape costs less than the cards.4. It requires less storage space for data and therefore has a large capacity.

5. It is reusable i.e., the old data can be wiped out and fresh information could be recorded on it.

6. The speed of transferring the data is very high comparing to paper devices.

Disadvantages:1. In magnetic tapes, the data has to be accessed sequentially. This makes the retrieval

of data slow.2. The punched cards can be read visually, whereas to read the magnetic tape a

machine is needed.3. The tape is subject to the usual wear and tear of time.4. Data will be erased if the tape is exposed or placed nearby any Magnetic field or high

voltage circuits.Using these devices, the data are entered onto the computer to get meaningful

information. The most commonly used input devices are magnetic disk, floppy disk, electronic keyboard, visual display unit and mouse.

Magnetic Disk:

The magnetic disk has an advantage over the magnetic tapes i.e., the data stored on a disk can be read randomly while in the magnetic tape, the data are read sequentially. The Random access is that the particular record in a file can be detected directly and the access time is saves. In magnetic disk the record is accessed in a fraction of second i.e., less than 0.01 sec.

The disks varying in diameter are generally coated on both sides with magnetic oxide. Each surface of the disk is divided into a number of sectors, called storage segments. The storage segments are a specific portion of a specific side of the disk. A segment can store one or more record of a file, which will vary according to the size of the record. While searching, a particular record can randomly be selected and directly accessed, because, each storage segment is uniquely marked by an address with side number, track, sector number etc.

Advantages:i) Direct access of data is possible. The data can be retrieved almost instantly.ii) The disk is more durable than the tape. This reduces the chances of loosing data.iii) The storage capacity of the disk is large.

Disadvantages:i) The disk come in packs and a disk pack is heavy. So, it is difficult to transport disks.ii) It requires more sophisticated hardware and operating systems than any of the earlier

mentioned input devices.

Floppy Disks:

This storage medium consists of a circular piece of thin plastic material, approximately 8 inches in diameter that is coated with an oxide material. The circular piece of plastic called a disk is enclosed in a square protective jacket with a cut out so that the magnetic surface is exposed. When inserted in the appropriate hardware device, the disk is rotated inside the protective jacket, allowing keyed data or data from main memory to be stored on the rotating disk. Once data is stored on the disk, it can be read from the disk into main computer. This medium for input and auxiliary storage called a floppy disk or disk.

Disks are available in a number of different sizes. Although the original disk was of the size of 8 inches, most personal computers now a days use a disk 51/4 inches in diameter. Even smaller sized disk approximately 31/2 inches in diameter are also available. Regardless of the size of the disk, the method of storing data is essentially the same. Each disk is divided into concentric circles called tracks. Each track is further divided into number of sectors. Data is stored on disk, in tracks, the number of which varies from computer to computer. The most commonly found configurations are 40 tracks, 72 tracks and 80 tracks.

To read data stored on disk or to store data on disk it is inserted in a disk drive. The large center hole fits over a hub mechanism, which positions the disk in the unit. The disk within the protective covering is rotated at approximately 300 to 600 revolutions per minute. To read or write data, a read/write head in the disk drive rests on the surface of the rotating disk, sensing or generating electronic impulses representing bits to be read or recorded. Characters are stored on a disk as bytes in the same manner as they are stored in main computer memory. To read data from the different tracks, the read/write head moves from track to track.

Compact Disk (CD) Drive:The Compact Disk (CD) used in a PC is similar in shape and size to the audio CD. The

Computer CD can hold about 650 MB of data. The computer CD is used to lead computer programs and other data in the hard disk of a PC. Most of the new computer programs are now available only on CDs. Some times programs are directly run from the CD. Also sometimes the PC may directly read the data stored on the CD at the time of running a program.

Most of the CDs are read only type. That is, the CPU can read information stored on a CD, however, it cannot store (write) any information on CDs. However, writable CDs are also available. Therefore, if a PC has a CD drive that has writing capacity, you can store information on a writable CD. So, normally the CD drives works as an input device, but it can also act as an I/O device.

Hard Disk: There are one or more platters or disks mounted with a common spindle. Each platter has two magnetic surfaces, top and bottom which is divided into sectors and tracks. The head is available between the platters to read/write data.

Systems Software

Software that controls the computer and enables it to run applications software. System software which includes the operating system, allows the computer to manage its internal resources.

Systems software consists program that start up the computer; load, execute, store, and retrieve application programs; store and retrieve files; and perform a series of utility functions. So system software is of three basic types. They are

Operating systems Language translators Utility programs

User

Documents Worksheets Database Applications

Operating System:

An OS is the principle piece of systems software in any computing system. The OS acts as an interface between the user and hardware.

Language Translator:A language translator is software that translates a program written by a programmer

in High Level language such as BASIC into machine language, which the computer can understand.

Utility Programs:Utility programs are generally used to support or enhance or expand existing

programs in a computer system.

Operating System Functions:

Operational systems are available for both personal computers and larger computers such as mini computers and mainframes. The functions include Booting: it refers to the process of loading an operating system into a computer’s main memory from floppy disk or hard disk. This loading is accomplished by a program called the ‘Bootstrap loader or Boot routine’ that is stored permanently in the computer’s electronic circuitry, other programs are called ‘diagnostic routine’ also start up and test the main memory, the CPU and other parts of the system to make sure they are running properly (‘Testing RAM’). Finally, other programs (indicated on your screen as ‘BIOS’) will be stored in main memory to help the computer interpret keyboard characters or transmit characters to the display screen or to a floppy disk.

Housekeeping TasksOne example of housekeeping task is formatting floppy disks. Formatting or

initializing electronically prepares a floppy disk so it can store data or programs. Other housekeeping tasks are

Operating System

Utility Programs

Language Translators

Word Processor

Spreadsheets DBMS a/w

Copy – or duplicate files and programs from one disk to another Backup – or make a duplicate copy of, the contents of a disk Erase-you can erase or remove, from a disk files or programs that are no longer

useful Rename-you can rename, or give new file names, to the files on a disk

User Interface:

User Interface or shell is the part of the operating system that allows you to communicate, or interact, with it. There are 3 types of user interfaces, for both operating systems and applications software

Menu Driven: A menu driven interface allows you to choose a command from a menu. A software menu offers you options to choose from – in this case, commands available for manipulating data, such as Print or Edit. Two types of menus are available: ‘Menu bars’ and ‘Pull down menu’.

Command Driven: Here we are using commands through our CUI (character User Interface)

Graphical User Interface: The easiest interface to use, the graphical-user-interface (GUI), uses images to represent options. Some of these images take the form of icons. ‘Icons’ are small pictorial figures that represent tasks, functions, or programs.

External Utility ProgramsUtility programs provide services which are not provided by other systems software.

They include screen savers, data recovery, backup, virus protection, file fragmentation, data compression, and memory management.

Screen Saver: It is a utility that supposedly prevents a monitor’s display screen from being etched

by unchanging images.

Virus:A virus consists of hidden programming instructions that are buried within other

programs which affects the system.

Fragmentation:It helps to manage memory more efficiently by moving the unused space to one end.

Data Compression:

It removes redundant elements, gaps, and unnecessary data from a computer’s storage space so less space is required to store or transmit data.

Memory Management:Utilities are programs that determine how to efficiently control and allocate memory

resources.

Application Software

It refers to software which perform application oriented or related function on a computer. Application software can either be purchased or can be developed using application development tool.

Two categories of application software can be purchased-

Specialized prewritten application software packages: Perform application – specific tasks which fulfill the needs of the user. For example, a specialized prewritten application software package could be purchased to prepare the payroll for a firm. The package would perform all the tasks required by the user, including writing checks and preparing government reports.

Generalized prewritten application software packages: Perform specific tasks, but can be used for many different applications. For example, a word processing application package can only be used to perform word processing functions. Thus, using the same word processing package, letters can be written by the accounting department to people who are late in their payments, by the marketing department to prospective customers, and by the president of the company to the stock holders

Application s/w development tools allow the user or the professional information processing analyst or programmer to develop the application software. These application s/w development tools must be purchased. They fall into one of two categories:

1. Fourth – generation software development tools.2. Programming languages

Under the first category ‘Electronic spreadsheet s/w’ is a s/w development tool which allows the user to develop a spreadsheet that contains both data and formulas.

Second s/w tool that is quite useful is file management s/w. The purpose of file management systems (sometimes called Database Management Systems) is to allow users to define files, records, data elements and to provide convenient method of access, update and create reports form the data.

Programming languages are C, FORTRAN for scientific purposes and C++, COBOL etc are used for commercial purpose application s/w tools.

Programming languages:

The computer being an electronic machine understands only the electric circuitry. It does not understand any of the languages that are used in our daily life. However, if we send an instruction to computer by the specified words, which it could understands, it will prove the power of computers. The specified words are the electronic signals that have only ones or zeros, and the machine code is written on it.

Programming languages are the part of the software or programming aids provided by the manufacturer. It is a language used in writing programs to direct processing steps to be carried out by a computer. The operations of the computer are controlled by instructions. Instead of setting switches as with conventional instruments, the user can select a sequence of computer operation and processes by entering instructions through the same input device through which data is entered.

Machine LanguageIt is important to understand the basic features of a computer program. A ‘Computer

Program’ contains a series of instructions, which directs the computer to perform those tasks necessary to process data and produce a desired output.

The language made out of binary digits (bits) 0’s, 1’s is known as machine language i.e. this is the language which is understood by the computer directly without using

translator. A combination of 8 bits represents a specific alphabet, a number, a character. The zero’s and one’s are the symbolic representation of absence and presence of electric pulses. ‘1’ represents the presence of electric pulse and ‘0’ represents the absence of electric pulse.

Two systems of coding have been used in the machine language. ASCII code (American Standard Coder for Information Interchange) EBCDIC code (Extended Binary Coded Decimal Interchange Code)

Example : ASCII EBCDICFor A = 10000001 For A = 11000001 B = 100000010 B = 11000010 C = 10000011 C = 11000011

An instruction prepared in any machine language has two parts1. Operation Code2. Operand (or) address

The first part is operation code. It tells the computer to perform certain function. The second part is the operand, which tells the computer to process the data. The programming for the first stored program computers was performed in machine language. Since machine language programming was a difficult, burdensome, and error – prone task, programming languages were developed to facilitate the coding process.

Advantages of Machine Level Language Efficiency at run time:

The computers can execute programs written in the machine language very fast because CPU directly understands machine instructions and no translation is required

Disadvantages: Machine Dependant: Machine language differs from computer to computer. The

design and construction of ALU, Control Unit and size of the memory determine it. Difficult to write the programs: Machine level language programs are difficult to

write because programmer has to memorize all the code number of the alphabets, numerals, special character and commands.

Error: To write a program in machine language the programmers have to remember the operation codes and operands. It becomes very difficult for the programmers to concentrate fully on the logic of the problem. The result is program errors.

Difficult to modify: It is very difficult to modify or correct the machine language programs.

Time Consuming: Writing a program in a machine language is a time consuming one and very tedious.

Assembly Language

The first programming languages were symbolic programming languages, commonly called ‘assembler languages’. Since writing instructions in a machineLanguage is difficult; these developed another language during second generation called as assembly language. The assembly language use’ mnemonic codes’. The mnemonic codes are the short form of English words.

Example:ADDITION – the mnemonic code is ADDSUBTRACTION – SUBLOAD – LDMOVE – MVCEDIT – ED etc.,

An assembler language program consists of a series of individual statements or instructions, which directs the computer to carry out the processing that is to occur. An assembler language statement consists of three parts.1. A Label 2. An operation code 3. One or more operands

As the computer cannot understand any language other than machine language (0,1) the assembly language have to be translated into machine language. This is done with the translator program called assembler.

Advantages: Simple to understand and to use Easy to write and modify the programs Time consuming Easy debugging

Disadvantages:

Machine dependent Knowledge of hardware is required to write and assembly language program More number of statements is required to write a simple program Programming are difficult and time consuming one when compared to high level

language Assembly language program cannot be executed directly by the computer

High Level Language

A programming language in which the program statements are not closely related to the internal characteristics of the computer is called a high-level programming language

The high level language is written using English like words and mathematical symbols such as COBOL, which is used for business applications. A high level language allows users to write in a familiar notation, rather than numbers or abbreviations. Most high-level language is not machine dependent – they can be used on more than one kind of computer. Examples of familiar languages of this sort are FORTRAN, COBOL, BASIC, Pascal, C and Ada.

Assembly Level Language

Assembler Machine Level Language

Assembly language requires an assembler as a language translator. The translator for high-level languages is, depending on the language, either a ‘compiler’ or an ‘interpreter’.

Compiler:A compiler is a language translator that converts the entire program of a high-level

language into machine language. The high level language is called the source code. The compiler translates it into machine language, which in this case is called the ‘object code’. The significance of this distinction is that the object code can be saved.

Interpreter: An interpreter is a language translator that converts each high-level language

statement into machine language and executes it immediately. No object code is saved, as with the compiler.The third generation, high-level languages are also known as procedural languages.

Advantages: To write the program in high level language is very easy Errors can be easily removed Software can be developed easily Commands one similar to natural languages

Disadvantages

The program written in high-level languages takes more time to execute More storage space is required Translators are required to translate high-level languages into machine level

language

Note: Difference between High-level languages, Assembly language, Machine level

languages refers the class notes.

Flowchart

Flowchart is a design tool. It is the diagrammatic representation of step by step procedure in program execution. Before a system or software is developed it is partitioned into subsystems or programs .Each program is coded independently and finally integrated to finished software.

One of the most widely used devices for designing programs is the flowchart, which graphically represents the logic needed to solve programming problem.

A program flowchart represents the detailed sequence of steps, needed to solve the problem. Program flowcharts are frequently used to visualize the logic and steps in processing.

Types of Flowchart:

System Flowchart:

It is the representation of the entire system. It shows how the system is divided into programs, the link between programs and hierarchy of programs.

Programme Flowchart: It is the representation of the processing or flow of individual programs.

Flowchart uses the following symbols:

This oval symbol is called as terminal symbol which indicates the beginning and ending of a process.

This is the Input/output symbol which is used to get an input and display an output.

This is the process symbol which indicates the processing done.

This is the decision symbol which executes a condition and based on the result has two paths (yes/no).It is the only symbol which has two exits

This is the connector symbol to connect the symbols

Example:Find the greater of 2 numbers:

Yes

No

Start

Read A,B

Is A > B?

Print A is big

Print B is big

Advantages: There is a standard designing a flowchart. It is easy to understand since it is in visual form.

Disadvantages: It is difficult to modify. Flowchart package is needed Structured design elements are not implemented.

Symbol The Input /output symbol is used to represent any input or Output operation. It may represent the point in a program

where the data (input) is required or where the information (Output) is to be displayed.

The process symbol represents some type of data Manipulation or arithmetic operation.

The decision symbol represents a logical comparison operation. Based on the comparison operation. Based on the Comparison, one of the two paths will be taken.

The connector symbol is used when several symbols displayed at one point might cause confusion and reduce understanding. The Symbol directs the reader’s attention to another area of the Flowchart where the programs flow continues.

The predefined process symbol is often used to represent a process that is used several times in the same program. This process is defined only once and reference by this block thereafter.

The annotation flag symbol is used to identify clarifying comments to other symbols. They do not represent a logical step or calculations in the program. They are used only for documentation purpose.

The terminal symbol represents the start or end of a program. It is also used to indicate a program interruption point where information can enter or leave.

The direction of flow symbols indicates the next step in the program.

Stop

Start

Open data file for input

Read data for an Employee

B

Is there data?Close data file

Stop

A

Is Gross Pay >300Tax rate is 15%

Tax rate is 10%

Calculate deductions & Net Pay

Print Paycheck

Read Data for an employee

BCalculate Gross Pay

Is there overtime Calculate overtime pay

1

2

3

4

56

78

9

10

11

122

Yes

No

YesNo

The flow charts shown in figure shows how the employee’s salary is calculated and paychecks are printed. The explanation of the flowchart is given below.

1. This opens the employees’ personnel file.2. This reads the employee’s last name, first name, week ending data, hourly pay rate

etc.3. This is the “Last record” decision point. If the answer is “yes” the program proceeds

to calculations.4. This multiplies hours worked with pay rate to get gross pay.5. This asks if the employee worked overtime.6. If the answer is “yes” overtime pay is calculated and added to gross pay.7. This asks if the gross pay for the week is above Rs 300.8. If the answer is “Yes” a tax rate of 15 % is calculated.9. If the answer is “No” a tax rate of 10% is calculated.10. This calculates the subtracts deductions, such as union dues and other taxes and

computes net pay.11. This prints out the employee’s paycheck.12. This reads the employee file for the next employee-name, week ending data, hourly

pay rate, etc.13. When all the employee files have been read and the answer to the “Last record”

decision is “NO”, the program begins to terminate.14. This closes all the employee’s personnel file.15. This stops the program.

Flowchart to print Paychecks

System Flowcharts:

In this text, most of our designs have dealt with isolated program, but in reality most programs are designed and used as part of a broad interrelated system of programs in which the output from one program may be the input to another program. As designers we must consider not just the specifications for the particular program segment on which we are working but also the specifications for the entire system in order to be sure that our segment fits in to the system as needed. A system flow chart shows how the programs fit together.

The system flowcharts looks at first very much like a program flowchart but there are two major differences first the program flowchart shows the detailed steps in a program and the system flow chart shows the same program as one process box without showing any details. Second the program flowchart uses the same symbol for all types of input and output with a system flowchart, we need to show more information the particular input/output hardware device must be shown to issue compatibility within the system. So the system flow chart utilizes a wide variety of input/output symbols to identify the medium (Disk, Tape, Keyboard) used.

The main symbols used in a system flow chart are shown below.

Program Box

Communication Link Flow line to Remote Device

Flow Line

Manual Operation

Magnetic Tape (I/O)

Magnetic Disk (I/O)

Document (Output)

Yes

Input Edit Program

Corrects Errors

EmployeeFile

EmployeeFile

Error Report

Video Display (Output)

Keyboard (Input)

Most of us are accustomed to the grocery checkout scan system that reads the UPC from product packaging and display the price on the cash register. That system is checking some form of on-line storage for the price and as the same time modifying the inventory count to indicate that one item has been sold. The inventory file can also be sued as input for a product ordering program that will produce printed recorder forms. A typical system flow chart might look something like the one on the next page.

Notice that we have shown the particular hardware used for input and output. This system is a simplification of a true point of sale inventory system. But you can see how the system flow chart clarifies the relation between programs. You can see in the above chart for e.g. that both the cash register program and the recorder program use the inventory disk file the system flow chart does not replace a program design. It is a supplements that shows another new which is not available from a program flowchart or pseudo code to see that details happening within one of the programs we would record to have a program design.

System Flow Diagram

Menu Display

Used Input

Code Input

Steps in developing a computer program

Because of the complexity of writing large business or scientific programs, it is important that the programmer approach writing a program in a systematic disciplined manner. Toward this end, a “program development cycle” has been established. The program development cycle consists of six basic steps:

1. Review of program specification2. Program design3. Program coding4. Program testing5. Program Maintenance6. Program documentation

Review of program specificationsThe first step in the program development cycle. These specifications normally

contain record and screen formats, printer spacing charts, database schemes and access requirements, system flowcharts and data flow diagrams, and a written narrative, which provides a detailed description of the processing that is to occur.

It is extremely important that the programmer thoroughly understand all of the various aspects of the problem to be solved. These aspects include the output to be produced, the input that is available to produce the output, the data in the database which is to be used in the production of the output, and the processing that must occur to produce the output.

At the end of the review of the system and program specifications, the programmer should completely understand the processing is to be performed what data is to be processed, and how the output is to be derived from the data available to the program.

Program Design

PriceDisplay

PriceFile

Cash RegisterProgram

Register Receipt

InventoryFile

RecorderProgram

RecorderForms

The design phase of the program development cycle is one of the most important. If a program is properly designed, it will be easily implemented in code in the selected programming language. At the end of the design phase, the structure and logic of the program should be detailed in such a fashion that the resulting program code from the design will be efficient, and will always produce correct output (reliable), will work under all conditions (robust), and will be easily modified (maintainable).Program design is done through tools such as Flowcharts, DFD etc.

Program coding

After the program has been designed, it must be coded, tested, and documented. The programming language used to code a program will normally be determined by the system analyst or project manager based upon the software available, the knowledge of the programming staff, and the standards established with in the information systems department.

Coding begins after the program has been designed. Coding the program involves the actual writing of the detailed programming statements. Each programming language has its own ‘syntax’, or coding rules, which must be followed. The programmer must follow these rules explicitly, or the program will not compile and execute as intended.

After the program has been coded (or in large programs, as the program is coded), a walkthrough provides the opportunity for other programmers to review, on a line for line basis, the coding developed by the original programmer.

Particular attention should be paid to ensuring that the code implements the design logic as expressed by the flowchart or psuedocode that the program is well documented, that the coding is free of errors, and that the coding is easy to read, leading to a program that is easy to modify and maintain.

Once it is agreed that the program code is well written and correctly implements the design of the program, the source program must be prepared for processing on the computer.

Program TestingAfter the program has been coded, it must be tested to ensure that it processes data

properly and produces the correct output. The basic procedures of testing a program are:

Test data is created with which to test program. Creating test data with which to test a program is an important responsibility of a programmer. The development of adequate test data, together with good program design and coding, are the most important tasks accomplished by a computer programmer.

The program is compiled and all diagnostic errors are removed The program is tested. If an interpreter is used, steps 2 and 3 occur together. Any errors, which are found in the program, are corrected, and the testing

continues until the program is certified as error-free. The program can be used in a system test to ensure that all programs within a

system work properly together

Testing Sequence:The programmer should develop a test plan which, among other things, specifies the

number of test runs to be executed, the portions of the program that are to be tested on each run, and the objectives of each test run

Stub Testing:

Testing only a portion of a program to ensure that it works properly is normally good testing strategy. This strategy, called ‘stub testing’, allows a program to be partially coded and tested before testing could be started. With stub testing, testing can begin shortly after coding is begun; with the result that program testing is spread more evenly across the project time, and management can review the progress of completed portions of the program.

Program efficiency:Consists of two elements: 1. The amount of main computer memory required to store the program when it is

processing data 2. The amount of time required by the program to process data. Program efficiency is directly affected by a program design and program coding. A well designed and coded program is not only understandable and easy to modify and maintain, it is also efficient with respect to the amount of main computer memory required and the speed with which it process data.

Program DocumentationThe documentation of each program developed in an information systems

department should include the following:

1. An abstract and general description of the purpose of the program2. Records layouts for report output, terminal output, files on auxiliary storage, user

views of data bases used, and any other data which is necessary in the execution of the program

3. A system flowchart, illustrating where the particular programs filts within the system4. A detailed description of the processing, which occurs within the program.5. The structure or hierarchy chart of the modules within the program6. The logic utilized within each module of the program. This logic should be illustrated

either through the use of flowcharts or through the use of Pseudocode.7. A listing of the source program8. A listing of the test data used to test the program and the results of the testing9. A console run form which includes the job control statements and any other

information necessary to specify how the program is to be run on the computer10. Users guide on how to use the program. This guide may include what data is used in

the system; the way to prepare source documents; and, in interactive programs, the manner in which to establish contact with the computer and interact with the program.

Program Maintenance:Program maintenance can be required to correct errors in a program. It can also be

required to make enhancements to a program, such as adding new features to a word processing program. These are the steps involved in developing a program.

UNIT-4

Operating Systems:

Operating System is a collection of programs, which interfaces between the user or application programs and the computer itself to control and manage the operation of the computer. Operational systems are available for both personal computers and larger computers such as mini computers and mainframes.

FUNCTIONS OF OS:

(1) The functions include Booting: it refers to the process of loading an operating system into a computer’s main memory from floppy disk or hard disk. This loading is accomplished by a program called the ‘Bootstrap loader or Boot routine’ that is stored permanently in the computer’s electronic circuitry.

(2) Other programs are called ‘diagnostic routine’ which starts up and test the main memory, the CPU and other parts of the system to make sure they are running properly (‘Testing RAM’). Finally, other programs (indicated on your screen as ‘BIOS’) will be stored in main memory to help the computer interpret keyboard characters or transmit characters to the display screen or to a floppy disk.

(3) Housekeeping TasksOne example of housekeeping task is formatting blank floppy disks. Formatting or

initializing electronically prepares a floppy disk so it can store data or programs. Other housekeeping tasks are

Copy – or duplicate files and programs from one disk to another Backup – or make a duplicate copy of, the contents of a disk Erase-you can erase or remove, from a disk files or programs that are no longer

useful Rename-you can rename, or give new file names, to the files on a disk

(4) User Interface:User Interface or shell is the part of the operating system that allows you to

communicate, or interact, with it. There are 3 types of user interfaces, for both operating systems and applications software

Menu Driven: A menu driven interface allows you to choose a command from a menu. A software menu offers you options to choose from – in this case, commands available for manipulating data, such as Print or Edit. Two types of menus are available: ‘Menu bars’ and ‘Pull down menu’.

Command Driven: Here we are using commands through our CUI (character User Interface)

Graphical User Interface: The easiest interface to use, the graphical-user-interface (GUI), uses images to represent options. Some of these images take the form of icons. ‘Icons’ are small pictorial figures that represent tasks, functions, or programs.

(5)Resource Management:The OS also manages computer resources such as memory, printer etc .and

allows the user to share the resources.(6)Memory Management:

The OS manages the allocation of memory to programs using several methods like Contiguous Memory allocation, page memory etc.It also swaps programs from main memory to Secondary storage and vice versa.(7)Process Management

The OS performs process scheduling i.e allocation of the processor for the execution of the programs. It uses algorithms like FIFO .

There are two types of operating system

1. Single User OS:In a single operating system only one person can use the computer at a time. Example: DOS

2. Multi User OS:

A multi user OS manages the allocation of computer resources among many users and are allowed to use the computer at the same time. CPU is shared by many users in multi-user operating system.Example: Unix, Windows NT, Windows 98 etc.,

UNIX:UNIX is a multi-user, time-sharing operating system. Ritchie and Thompson originally

wrote it at the Bell Telephone labs in 1973 for a small PDP 11 Computer. They used a high-level language C to write UNIX. It is very popular as it was written in C and thus portable.

Architecture of UNIX:

The UNIX OS can be bought of as a layered system. Unix Kernel controls the resources of the computer and allocates it among users. It controls peripheral devices such as disks, printers etc., connected to the computer. It provides user with file systems to store data and programs. It lets users run their programs by proper memory allocation and management.

In the next level of UNIX provides a command interpreter called ‘Shell’. There are large no. of very useful commands provided by shell. Users can create a series of shell commands and store it in a file. This file can be made as executable file and when invoked will act like a new shell command.

Unix also provides a very interesting idea called a pipe. A pipe is a way to send the output of one program as the input of another program without storing the output of the first program in a temporary file. A pipeline is a connection of two or more programs through pipes. There are large families of UNIX shell programs that read an input, perform a single transformation, and write an O/P.

For example:

Grep Command - which searches a file for lines that match a given pattern and O/P’s them. Sort Command - Sorts the file as per some specifications.Such commands are called filters.

A part from filters provided by the system, user could create his own filter by combining shell commands.

The outermost layer of UNIX has language compliers for C, FORTRAN 77 etc.

Advantages:

1. A unique feature of the language compilers in UNIX is that it provides a commonObject code format, which allows easy mixing of high-level languages.

Shell

KernelH/W

2. UNIX has some good text processing programs. Many additional utilities such as calendar, games, graphics etc are available.3. Multi-User built in networking capabilities, the ability to run multiple tasks at one time, and versions that can run on all kinds of computers.

Other Unix based OS are Next step from Next Inc. Solaris by Sun Microsystems etc.

DOS-Disk Operating System:

DOS runs primarily on IBM and IBM compatible microcomputers, such as Compaq, zenith computers, Dell Computers and Gateway.In earlier stage there are three kinds of DOS

1. MS-DOS: it is from Microsoft Corp. The latest version of this is 6.22.2. PC-DOS: it is from IBM. The latest version of this 6.1.3. DR-DOS (or) Novell’s DOS-for network software from Novell Inc acquired with

DR(Digital Research) upgraded it and renamed it Novell DOS 7.

The Most recent versions are all backward compatible. Backward compatible means that users can run the same applications on the later versions of the OS that could run on earlier versions.

Recent versions of DOS have explained the range of the operating system. For example, version 4.0 changed MS-DOS from a command driven interface to a menu driven interface, version 5.0 added graphics-based interfaces. Version 6.0 added features that tools advantage of a computer’s main memory. It also used data compression to double the amount of information that could be stored on a hard disk drive.

The DOS built a limitation up to one-MB memory. To exceed this limit we need special memory system called EMS(Extended Memory System).

Disadvantages:

1. Command driven OS.2. Single user programmable OS.

In Dos we have 2 types of commands.

External Commands:

External commands require certain special DOS files or being executed. Example: Auto.exe, COMMAND.com, FORMAT, PRINT, TREE, SYS, etc.,

Internal Command:

Internal Commands are already present in Dos and brought into the memory as soon as the computer is switched on.

Example: COPY, DEL, DIR, TYPE, MKDIR, CD, RD, DATE, TIME etc.,

WINDOWS OPERATING SYSTEM:

Windows is an operating environment. It is the extension of the disk operating system. Windows is system software. It requires DOS to run the application programs. The DOS should be loaded into the memory before the window is executed. After the

windows is loaded into the memory the windows environment takes all the device controls. It also takes care of the memory management of the programs run by the windows software.

Windows 98:

Microsoft’s desktop operating system dominance is mainly due to one operating system-window. Windows was a 16-bit operating system (windows 3.x) till the introduction of Windows 95. Now the latest version of windows-windows 98- has been released with lot of more features and integration with the Internet.

Windows 98 makes your computer easier to use, with new and enhanced

FEATURES:

1. WEB INTEGRATION:Windows 98 is easier to use with true web integration and workflow

enhancement such as icon highlights, forward and backward buttons and an easy-to-customize START menu.

2. MULTIPLE DISK SUPPORT:Multiple disk support makes it possible for you to use several monitors

simultaneously to increase the size of your desktop, run different programs on separate monitors, work with various resolutions and run programs or play games with multiple views.

3. POWER MANAGEMENT:“On Now” makes your computer more responsive by improving startup time.

Using power management techniques, on now can start your computer in just a few seconds and restore all your programs where you left them. In addition, it allows your computer to continue working even though it appears to be turned off. You can leave all of your programs running, download your favorite web pages, send and receive e-mails, backup your hard disk, or tune-up your operating system without being at your computer.

4. UNIVERSAL SERIAL BUS:The Universal, serial bus (USB) makes your computer easier to use with

advanced plug-and-play capabilities. Using a new, universally standard connector, you can add device to your computer easily without having to restart.

5. ACCESSIBILITY WIZARDS:The accessibility wizard makes it easier for people with disabilities to operate

a computer without installing special software. Accessibility option-such as sticky keys, show sound, and MouseKeys-are designed to help user with specific disabilities make full use of computer.

6. HELP:Windows 98 includes a new help system that makes your computer easier to

use. With help, you can find answer to your questions quickly and easily. You can also get up-to-date technical support from World Wide Web.

Widows 98 import your computer reliability by introducing new wizards, utilities, and resources that help keep your computer system running smoothly.

1. WINDOWS UPDATE:Windows update, Microsoft’s new web-based resource site, automates driver and system file updates, and provides up-to-date technical support.

2. SCAN DISK:Scandisk runs automatically in the event the operating system is shutdown improperly. Scandisk detects corruption when they are most likely to occur and then corrects them.

Windows 98 includes a suite of programs like Maintenance wizard, Drive, Converter, Disk Defragmenter, etc. Designed to optimize your computer’s efficiency, especially when used together.

Windows 98 includes a mail icon that launches your default e-mail programs. Outlook express provides you with secure and personalized features for e-mail and newsgroups communication. With net meeting you can hold the digital conversation with family, friends and business associates around the world without spending a fortune.

Net meeting also makes it possible for you to work with a group of people from within any windows-based program by drawing on a shared white board, sending text messages, and transferring files. Windows 98 includes front-page express, a web-page editor that give you full access to the power of in a familiar, easy-to-use desktop interface.

Windows NT:

The Windows NT (New Technology) is one of the most powerful operating system for business computing. The Windows NT combines the ease of use of Windows 95 with the power and reliability of Windows NT.

Features of Windows NT:

1. Easy of use, Productivity and Compatibility:Windows NT workstation has the Windows 98 easy to use interface, which helps you, work easier and faster. Windows NT ensure high performance for 32 bit programs and have the preemptive multitasking capabilities of Windows NT and can run in separate address space for better responsiveness and reliability.

2. System Reliability and Data Protection:Window NT Workstation meets the reliability, a standard required by MIS Professionals and other users to run critical line-of-business programs. Windows NT workstation protects application programs from one another.

3. Workgroup and Networking support:Built-in file sharing and print-sharing capabilities make it easy to use for workgroup computing. Windows NT has an open networking system interface that is compatible with banyan VINES, Netware Novell, UNIX etc.

4. Object Linking and Embedding:In Windows NT you can combine information from several application into one compound document using the special object linking and embedding (OLE) capabilities.

Internet:

The Internet is a computer network made up of thousands of networks worldwide no one knows exactly how many computers are connected to the Internet. It is certain, however, that these number in the millions and are increasing at a rapid rate.

No one is in charge of the Internet. There are organizations, which develop technical aspects of this network and set standards for creating applications on it, but no governing body is in control. The Internet backbone, through which Internet traffic flows, is owned by private companies.

All computers on the Internet communicate with one another using the transmission control protocol/Internet protocol suite, abbreviated to TCP/IP.Computers on the Internet use client/server architecture. This means that the remote server machine provides files and services to the user’s local client machine. Software can be installed on a client computer to take advantage of the latest access technology.

An Internet user has access to a wide variety of services: Electronic mail, File Transfer, Vast information resources, Interest group membership, and Interactive collaboration, multimedia displays, Real – Time broadcasting, Shopping opportunities, breaking news and much more.

The Internet consists primarily of a variety of access protocols. Many of these protocols feature programs that allow users to search for and retrieve material made available by the protocol.

Levels of Internet Connectivity:

Three Levels of Connectivity:Gateway Connectivity: Imagine a small network or BBS (Bulletin Board Service) that has nothing to do with Internet as such. But one of the computers on the network is hooked up to it. Thus this interaction point computer provides a gateway to Internet access for the rest of the network.

Advantages: Low cost of access as the cost is shared by the whole network. Even the existing non-IP (Internet Packet) based networks can be easily

connected.Disadvantages:

The network depends on the facility provided by the gateway.

AOL (American Online), Prodigy, VSNL-GIAS are the examples of gateway connectivity. Currently in India, VSNL gateway in providing E-Mail, FTP, Telnet, Chat & UNIX Prompt facilities to its subscribers.

Remote Access Connectivity:This type of connectivity is achieved through a dial-up terminal connection. The

mainframe on the Internet acts as a host using a dial-up connection. The host carries out commands typed at terminal. This is most widely used type of Internet connectivity.

Disadvantage: The problem associated with this level is that only the programs present at

the host can be executed.

Loading a new program or client does not provide the ability to execute it. Downloading a file from any site becomes a two-step process:

1. Downloading a file from any site.2. To transfer host to local terminal.

Direct Connectivity:This is most expensive type of connectivity is achieved by high-speed lines to go line

on the Internet. Internet is available round the clock. It is usually opted with heavy load and number of users using mainframe computers. This type of connection provided on demand by the service providers based on Point-to-Point protocol (PPP) or SLIP (Serial Line Internet Protocol).

Components of the Internet:

1. World Wide Web:

The World Wide Web (abbreviated as the Web or WWW) is a system of internet servers that supports hypertext to access several internet protocols on a single interface Almost every protocol type available on the internet is accessible on the web. This includes e-mail, FTP, Telnet and Usenet News. In addition to these, the World Wide Web has its own protocol: Hyper Text Transfer Protocol, or HTTP.

The World Wide Web provides a single interface for accessing all these protocols. This creates a convenient and user-friendly environment. It is no longer necessary to be conversant in these protocols within separate, command-level environments. The web gathers together these protocols into a single system. Because of this feature, and because of the web’s ability to work with multimedia and advanced programming languages, the World Wide Web is the fastest-growing component internet.The operation of the web relies primarily on hypertext as its means of information retrieval. Hypertext is a document containing words that connect to other documents. These words are called links and are selectable by the user. A single hypertext document can contain links to many documents. In the context of the web, words or graphics may retrieve as links to other documents, image, video and sound. Links may or may not follow a logical path, as each connection is programmed by the creator of the source document. Overall, the WWW contains a complex virtual web connections among a vast number of documents, graphics, videos, and sounds.Producing hypertext for the web is accomplished by creating documents with a language called Hypertext Markup language, or HTML with HTML, tags are placed within the text to accomplish document formatting, visual features such as font size, italics and bold, and the creation of hypertext links. Graphics may also be incorporated in to an HTML document. HTML is an evolving language, with new tags being added as each upgrade of the language is developed and released. The World Wide Web consortium, led by web founder Tim Burners-Lee, coordinates the efforts of standardizing HTML.The World Wide Web consists of files, called pages or home pages, containing links to documents and resources throughout the Internet.The Web provides a vast array of experiences including multimedia presentations, real-time collaboration, interactive pages, radio and television broadcasts, and the automatic “push” of information to a client computer. Programming languages such as java, java script and visual basic are extending the capabilities of the web. An increasing amount of information on the Web is served dynamically from

content stored in databases. The web is therefore not fixed entity, but one that is in a constant state of flux.

2. E-Mail:

Electronic mail, or e-mail allows computer users locally and worldwide to exchange messages. Each user of email has a mailbox address to which messages are sent. Messages sent through e-mail can arrive within a matter of seconds.

A powerful aspect of e-mail is the option to send electronic files to a person’s e-mail address. Non –ASCII files, known as binary files, may be attached to e-mail messages. These files are referred to as MIME attachments. MIME stands for multimedia Internet mail extension, and was developed to help e-mail software handle a variety of file types. For example, a document created in Microsoft word can be attached to an email message and retrieved by the recipient with the appropriate e-mail program. Many email programs, including Eudora, Netscape Messenger, and Microsoft Outlook Express, offer the ability to read files written in HTML, which is it a MIME type.

3. TELNET:

Telnet is a program that allows you to log into computers on the Internet and use online databases, library catalogs, chat services, and more. To telnet to a computer, you must know its address. This can consist of word (locis.loc.gov) or numbers (140.147.254.3). Some services require you to connect to a specific port on the remote computer. In this case type the port number after the Internet address.Example: Telnet nri.reston.va.us 185.

Telnet is available on the World Wide Web. Probably the most common web based telnet is available through telnet are library catalogs. A link to a telnet resource may look like any other link, but it will launch a Telnet session to make the connection. A telnet program must be installed on your local computer and configured to your web browser in order to work.

4. FTP:

FTP stands for File Transfer Protocol. This is both a program and the method used to transfer files between computers. Anonymous FTP is an option that allows users to transfer files from thousands of host computers on the Internet to their personal computer account. FTP sites contain books, software, games, sounds, multimedia, Course work, articles, images, datasets, and more. If your computer is directly connected to the Internet via an Ethernet cable, you can use one of several PC software programs, such as WS_FTP for windows, to conduct a file transfer.

FTP transfer can be performed on the World Wide Web without the need for special software. In this case, the web browser will suffice. Whenever you download software from a web site to your local machine, you are using FTP.

5. E-MAIL DISCUSSION GROUPS:

One of the benefits of the Internet is the opportunity it offers to people worldwide to communicate via e-mail. The Internet is the home to a large community of individuals who carry active discussions organized around topic-oriented forums distributed by e-mail. These are administered by software programs. Probably the most common program is the Listserv.

List servers cover a great variety of topics , many of them are academic in nature. When you subscribe to listserv, message from one subscriber is automatically sent to your electronic mailbox. You subscribe to a listserv by sending an email message to a computer program called a list server. List servers are located on computer networks throughout the world. This program handles subscription information and distributes messages to and from subscribers. You must have a e-mail account to participate in a listserv discussion group.

6. USENET NEWS:

Usenet News is a global electronic bulletin board system in which millions of computer users exchange information on a vast range of topics. The major difference between Usenet News and e-mail discussion groups is the fact that Usenet messages are stored on central computers, and users must connect to these computers to read or download the messages posted to these groups. This is distinct from e-mail distribution; in which message arrive in the electronic mailboxes of each list member.

Usenet itself is set of machines those exchanges messages, or articles from Usenet discussion forums, called newsgroups. Usenet administrators control their own sites, and decide which (if any) newsgroups to sponsor and which remote newsgroups to allow into the system.

There are thousands of Usenet newsgroups in existence. While many are academic in nature, numerous newsgroups are organized around recreational topics. Much serious computer-related work takes place in Usenet discussions. A smaller number of e-mail discussion groups also exist as Usenet newsgroups.

The Usenet news feed can be read by a variety of newsreader software programs. For example, the Netscape communicator site comes with a newsreader program called messenger. Newsreaders are also available as standalone products

7.CHAT and INSTANT MESSENGING:

Chat programs allow users on the Internet to communicate with each other by typing in real time. They are sometimes included as a feature of a web site, where users can log into the “chat rooms” to exchange comments and information about the topics addressed on the site. Chat may take other, more wide ranging forms. For example, America online is well known for sponsoring a number of topics chat rooms.

Internet Relay Chat (IRC) is a service through which participants can communicate to each other on hundreds of channels. These channels are usually based on specific topics. While many topics are frivolous, substantive conversations are also taking place. To access IRC, you must use an IRC software program.

A variation of chat is the phenomenon of instant messaging. With instant messaging, a user on the web can contact another user currently logged in and type a conversation. Most famous is America Online’s instant massagers. ICQ is another commonly used chat program.

Intranet:

System administrator will be there within the organization. All the people will be given an Identity No. If any mail comes top the person that will be given to him. Control is with the system administer, personal department can access only personal department and not production department control, system administer will control the system.

Advantages:1. Putting company related information on Net.2. Can be accessed by all employees of the organization in the office or via dial up access.3. Applications used are company procedure or manuals, corporate databases.4. It is the usage Internet Technologies within the organization to achieve better results that the conventional means of access and transfer.5. It should be noted that Intranet technologies could be used only if the network is within a single campus.

Extranet:

Extranet is connected with outside suppliers, customers. All suppliers will know when to supply and customers will know when they are produce goods.

It is the use of Internet technologies outside the organization boundaries to achieve better results than the conventional means of access and transfer.

Extranet technologies are common where companies experimented their boundaries to include their suppliers into their network.

E-mail Procedure

Step 1:The user types the document into the computer or selects the files that are to be mailed.

Step 2:The computer files are converted into a form that is suitable or transmission over the telephone lines using a modem.

Step 3:The files are transferred using the telephone connection to the local node of the E-mail service Provider.(ESP).

Step 4:The reverse process of step2 occurs and the analogy signals are converted back to digital form suitable for computer at the other end.

Step 5:As the files reach the local node of E-mail service provider, the computer sorts the files to be transmitted to different location.

Step 6: The ESP transmits the files using the microwave link(VSAT-very small Aperture Terminal) or some other means to the nearest node to destination.

Step 7: The ESP node nearest to the destination receives the files.

Step 8: The ESP node then resolves the address and prepares the file to be dispatched.

Step 9: the node computer of the ESP user the same device (modem) to connect the received signals back to analogs signals as a preparation to transmit them to the destination. Computer over telephone lines. Thus as can be seen, modem is a very important device not only in the case of E-Mail but the whole cycle of Electronic information exchange.

Step 10: The files are transferred over the telephone line to the destination computer.

Step 11: the modem then finally converts these into digital signals for the destination computer.

Step 12: the files reach destination and the user can read them. And reply forward or store them.

E-Commerce:

Electronic Commerce is one of the most important aspects of the Internet to emerge. It allows people to exchange goods and services immediately and with no barriers of time or distance. Any time of the day or night you can go online and buy almost anything you want. This is how e-commerce works.The consumer moves through the Internet to the merchant’s web site. From there. He decides that he wants to purchase something, so he is moved to the online transaction server, where all of the information he gives is encrypted. Once he has placed his order, the information moves through a private gateway to a processing network, where the issuing and acquiring banks complete or deny the transaction. This generally takes place in no more than 5-7 seconds.There are many different payment systems available to accommodate the varied processing needs of merchants, from those who have a few orders a day to those who process thousands of transactions daily. With the addition of secure socket layer technology, e-commerce is also a very safe way to complete transactions.

Mobile Computers:

Fixed point-to-point telephony is given way to global cellular mobile communication system. Such a system provides anytime, anywhere connectivity.

GSM-global system for mobile communication is a widely used mobile communication system.

GSM standard is optimized for short message service (SMS) that allows GSM mobile users to send and receive, short concise and abbreviated text message to other mgs.

SMS length of a single message is restricted. SMS message can be sending and received simultaneously with voice data and fax

calls. SMS message low bit rate signaling channel for message transmission.

SMS Features:

GSM is most popular mobile cellular network. It supports two way paging communication. It supports store-forward capability. Point to point short text message and cell broadcasting.

Radio Paging:

‘Paging service network’ provides for one way (receive only) message service. This means the mobile user cannot send a message. Such a service is also known as mobile terminated messaging.

Limitations:1. One-way service.2. Paging is restricted to particular city only, and does not provide to global

messaging features provided by SMS.

MOBITEX:

Is the popular and widely deployed cellular wireless data network in US.

1. It specifies both packet and circuit switched transmission facilities.

2.MOBITEX system offers store and forward capabilities. Each registered user has a mailbox in MOBITEX system. If a packet is undelivered, then at the sender’s discretion it can store in recipient mailbox.

M-Commerce:

E-commerce over mobile phones. It is a WAP application. WAP is a protocol by which the mobile phone accesses specific sites on the Internet and handsets need specific micro-browser s/w installed to search for WAP-enabled sites.

There are two forms of HTML programming.HTML for normal browsing and WML (Wireless Markup Language) for WAP application.

Limitations

Reduced or to disappear with increasing data rates delivered to the hand set (first from GPRS-General Packet Radio System and then UMTS-Universal Mobile Telephone System) and considerably improved displays. Japan’s I-mode handset to handle a compressed version of normal HTML pages rather than special WML pages.

UNIT-5

System: A System is a network of related procedure designed to perform some activity.

Procedures: Procedures are logical steps by repetitive action are initiated, carried forward, controlled, and finalized.

Systems, which are implemented using a computer, fall into 3 broad classifications.

Operational System. Management Information System. Decision Support System.

Operational System:

Operational System is designed to process the data that is generated by the day-to-day business transaction of companies. This SAD follows a well-defined scientific problem solving approach. The approach can be broken down into a series of phases:

Phases 1- Initiation of the system project & preliminary Investigation.Phases 2- detailed system investigation & analysis.Phases 3- System design.Phases 4- System development.Phases 5- System implementation and evaluation.Phases 6- System maintenance.

Initiation of the System Project & Preliminary Investigation:

A system project can originate in several ways, but a common way is that the manager of a user department contacts the systems analysis and design group in the information systems department with a request for assistance.

The purpose of the ‘preliminary investigation’ is to determine if the request for assistance, which has been communicated, to the system department warrants further detailed investigation and analysis. The most important aspect of the preliminary investigation is to identify if there is a problem and, if so, to uncover the true nature of the problem. The primary method of conducing the preliminary investigation is through the ‘personal interview’. The interviews are conduced with managerial and supervisory personnel who may have knowledge of the problem and system under study.

At the conclusion of the investigation, the analyst will present the findings to management and recommend the next course of action. If it is recommended to continue the project through a detailed investigation, the analyst will provide management with an estimate of the cost for the next phase in terms of man-hours, and elapsed time.

System analysis

If approval to proceed is obtained from management the analyst will begin the ‘detailed investigation and analysis’. This phase of the system study is divided into two parts: 1) A detailed investigation in which the emphasis is on WHAT is taking place in the current system: 2) An analysis of what is taking place with an emphasis on WHY the procedures found are occurring, and what the user sees as the requiem ends for a new system.

The basic fact-gathering techniques used during the detailed system investigation are: 1) The interview: 2) Questionnaires; 3) Gathering the current system documentation and operating forms; 4) Personal observation of current procedures.

Specific steps undertaken at this time to gather the facts include: 1) review the organizational chart of the structure of the company to determine who are the workers, supervisors, and management personnel associated with he system under study; 2) Conduct interviews with selected personnel to determine what is actually taking place in the current system, rather than what is supposed to take place according to the written rules of the company; 3) Obtain actual copies of operating documents; 4) Document and record all of the data flow within the currently existing system and the actual procedures, which are followed.

Once of the more effective is the data flow diagram. This DFD illustrates graphically the flow of data and the procedures used for an auto parts order entry system. Since the present system is being reviewed in detail, there obviously were some problems in the system. After the current system has been documented and analyzed, the analyst must assist the user to identify the requirements of the new system. This analyst will include understanding the problems in the current system, planning for growth and change in the user department, understanding the personnel requirements and capabilities in the department and a number of other factors as well.

At the conclusion of this activity the analyst should prepare a written and oral presentation of the findings, which can be presented to both the user and to other management.

System Design:

Upon approval to proceed, the analyst must determine the best method for implementing a new system. The choice usually are: 1) Personnel in the information systems department design and implement the application: 2) The user, through the use of fourth generation applicatio9n development tools or through the facilities offered by the information centre, designs and implements the application: 3) A prewritten applications software package is purchased which, with little or no modification, will perform the tasks required of the new system: 4) The systems department designs the system and then contracts with an outside organization to have the system programmed and implemented: 5) the entire project is contracted out to an outside organization that designs and implements the system.

As the design phase begins, develop a prototype of the new system. A ‘prototype’ is a series of small programs that allows a few of the transactions, with will be processed on the real system to be processed. Because of the prototype system, the user will have an exact idea or how the system will behave when it is implemented, and the analysts are ensured that when the system is developed and implemented, the user will be satisfied

When designing the ‘system output’ specific steps must be undertaken, including o/p requirements of new system types of output etc., The analyst must also, during the project maintain some data which will be stored by the system. This is called ‘Data dictionary,. An important aspect of the establishment only valid data is accepted and processed.

System Development:

After the design phase of the project, the project enters the “system development” phase. The major tasks common to all system projects during the system development phase are: 1) Establish a project development and implementation plan; 2) Develop detailed programming specifications; 3) Program and test the system; 4) Prepare final documentation of the system.

One of the first steps in the system in the system development phase is to develop a detailed schedule of each of the activities that is to be performed. The time schedule of the project is produced by a method often used to document the schedule is the bar or “Gantt chart”. (flg. Refer your notebook).

Programmer’s jobs are 1) review the program 2) design the program 3) coding the program 4) testing the program.

Program design entails the development of the structure of the program and than the development of the logic to solve the problem presented by the program.

After the programs in the system have been tested individually (commonly called ‘unit tests’) the entire system of programs must be tested as a whole. This process is called “System Testing”.

Implementation and Evaluation:

After testing has been complete and the documentation prepared, the system is ready to be implemented on the computer and run in a production environment. “Conversion” refers to the process of making the change from the old system to the new system. Two methods are direct conversion and parallel conversion.

With direct conversion, at a given date the old system ceases to be operational and

the new system is placed into use. Direct conversion, howere, can be risky, in spite of the great care, which may have been taken in designing the system.

Parallel Conversion consists of processing data on both the old and new systems simultaneously and comparing the results. Regardless of the method of implementation used. It is important to conduct a formal post implementation evaluation of the system. The evaluation consists the designing, operating costs.

System Maintenance:

An ongoing process after the system has been implemented is ‘system maintenance’. Maintenance consists of two major activities: 1) Changes to correct errors in the system: 2) Changes to give the system additional capabilities or to conform to government or company regulations.

Maintenance activities require a great deal of time for many programmers and analysts. Systems, which are well documented and contain well-designed programs, are much easier to maintain than those, which do not follow good documentation and coding standards.

Computer Based Information Systems:

Transaction Processing:

In most organizations, particularly business organizations, most of what goes on takes the form of transactions. A ‘transaction” is a recorded event having to do with routine business activities. This includes everything concerning the product or service in which the organization is engaged: Production, distribution, sales, orders. It also includes materials purchased, employers hired, taxes paid, and so on. Today in most organization the bulk of such transactions are recorded in a computer-based information system.

A transaction processing system (TPS) is a computer based information system that keeps track of the transactions needed to conduct business. The transaction processing system is also sometimes called an electronic data processing (EDP) system.Some features of a TPS are as follows:

Input and Output : The inputs to the system are transaction data: bills, orders, inventory levels, and the like, the output consists of processed transactions: bills, paychecks, and so on.

For lower managers : Because the TPS deals with day-to-day matters, it is principally of use to supervisory managers. That is, the TPS helps in making tactical decisions. Such systems are not usually helpful to middle or top managers.

Produces detail reports : A lower-level manager typically will receive information in the form of detail reports. A detail report contains specific information about routine activities. An example might be the information needed to decide whether to restock inventory.

One TPS for each department: Each department or functional area of an organization-Research & Development, Production, Marketing, and Accountings Accounting & Finance – usually has its own TPS. For example, the Accounting & Finance accounts payable, and payroll.

Basis for MIS and DSS: The database of transactions stored in a TPS is used to support a management information system and a decision support system.

Office automation:

Computer has helped automation of many industrial and business systems. They are used extensively in manufacturing and processing industries, power distribution systems, airline reservation systems, transportation system, banking systems and so on. Computer aided design and computer aided manufacturing are becoming popular among the large industrial establishment.

Management Information System (MIS)

A ‘management information system (MIS)’ is a computer-based information system that derives data from all on organization’s departments and produces routine reports of the organization’s performance. To perform it’s major functions of planning organizing, staffing, directing, and controlling.

Concept of MISPlanning

Planning means to set the goals and objectives for the company: management should know and understand the nature of the company. Its competition, its market place etc., before planning. Establishing policies, procedures, programs of a company are one of the important steps of planning.

Concept of MIS

Organizing To organize means to develop and maintain the resources and structure of a

company. Managers must be assigned their duties; workers must be given their work to meet the desired goal.

StaffingStaffing is a continuous process of recruiting and training the employees.

Directing To co-ordinate the activities of the company and to delegates the authority for

causing out the activities and to attain the Objectives directing is necessary. Directing includes Co-ordination, Communicating, motivating the employees to do their jobs to attain the goals.

Controlling

To control means to evaluate by comparing actual with the goal: Any deviation actions are taken to correct the deficiencies. Sometimes the necessary action requires written to the planning functions to revise the goals..MIS can be divided into various level of management.

Operational Level

Operational manager is responsible for day-to-day operations: The functions are employing the people, training to the employees, maintaining the stick level, maintaining the customer relationship-supervising the employees, and verifying the cash register.

Tactical Level:

Responsibility is given to the manager not for a single unit but for several units. MIS functions are to rectify the consumer complaints, to achieve the individual unit goals, to analyze and find the reason for decrease in sales and production.

Top Level or Strategic Level:Responsibilities given to the manager for the whole organization for long range

planning. It includes fixing the organization for long range planning. It includes fixing the objectives, scheduling the program to prepare the budgeting.

Decision Support Systems (DSS)

A decision support system (DSS) is a computer-based information system that provides a flexible tool for analysis and helps managers with non-routine decision-making tasks.Some features of a DSS are as follows:

Input and Output:

Inputs consist of some summarized reports, some processed transaction data, and other internal data. They also include data that is external to that produced by the organization. This external data may be processed by trade associations, marketing

research firms and other government agencies. The outputs are flexible, on-demand reports with which a top manager can make decisions, about unstructured problems.

Mainly for Top Managers:

A DSS is intended principally to assist top managers, although it is now being used by middle managers, too. Its purpose is to help hem make strategic decisions – decisions about unstructured problems, often unexpected and nonrecurring. These problems may involve the effect of events and trends outside the organization. Examples are raising interest rates or a possible strike in an important materials-supplying industry.

Produces Analytical Models:

The key attribute of a DSS is that it uses models. A ‘model’ is a mathematical representation of a real system. The models use a DSS database, which draws on the TPS (Transaction Processing System) and MIS (Management Information System) files, as well as outside data. The system is accessed through DSS software.

The model allows the manager can simulation-play a “what if” game-to Reach decisions. Thus, the manager can simulate an aspect of the organization’s environment in order to know how to react to a change in conditions affecting it. By changing the hypothetical inputs to the model-number of workers available, distance to markets, ir whatever-the manager can see how the model’s outputs are affected.

Group Decision Support Systems

As communications becomes a more important of an information system, so does a kind of an information system, so does a kind of DSS called group decision support systems. A ‘group decision support system’ (GDSS) enables teams of coworkers to use networks of microcomputers to share information and cooperate on projects. A group decision support system is also called workgroup computing. By sharing ideas, workers can build consensus and arrive are decision collaboratively. GDSSs are being found in fields ‘ranging from banking and insurance to architectural design and newspaper publishing.

Executive Information Systems

An Executive information system (EIS) is a DSS made especially for top managers and specifically supports strategic decision-making. An ESI is also called an Executive Support System (ESS). It draws on data not only from systems internal to the organization but also from those outside, such as news services or market-research databases. An EIS might allow senior executives to call up predefined reports from their personal computers, whether desktops or laptops. They might, for instance call up sales figures in many forms – by region, by week, by fiscal year, by projected increases. The EIS includes capabilities for analyzing data and doing “what-if” scenarios.

Artificial Intelligence (AI):

AI is a group of related technologies that attempt to develop machines to emulate human-like qualities, such as learning, reasoning, communicating, seeing and hearing.

Artificial Intelligence is a research and applications discipline that includes five areas:

Robotics – is concerned with developing machines that can perform work like o Humans.o Perception systems – are sensing devices that emulate the human senses.o Expert systems – are interactive programs that help people solve problemso Otherwise requiring a human expert.o Natural language processing (including fuzz logic) – studies ways

computers can understand human language, and fuzzy logic deals with problems of uncertainty.

o Neural networks – mimic human brain nerve cells. We also consider an area known as artificial life, which involves computer instructions that act like living organisms.

Expert Systems

An expert system is an interactive computer program that can apply rules to input in such a way as a generate conclusions. The program helps users solve problems that would otherwise require the assistance of a human expert.Note: Draw the diagram.An expert system consists of three components.

Knowledge base:

A “Knowledge bas’ is an expert system’s database of knowledge about a particular subject. This includes relevant facts, information beliefs, assumptions, and procedures for solving problems. The basic unit of knowledge is expressed as an IF-THEN-ELSE rule. Programs can have as many as 10,000 rules. A system called ExperTAX, for example, which helps accountants figure out a client’s tax options, consists of over 2000 rules.

Inference engine:

The ‘inference engine, is the software that controls the search of the export system’s knowledge base and produces conclusions. It takes the problem posed by the user of the system and fits it into the rules in the knowledge base. It then derives a conclusion from the fact and rules contained in the knowledge base.

Reasoning may be by a forward chain or backward chain. In the forward chain of reasoning, the inference engine begins with a statement of the problem form the user. If then proceeds to apply any rule that the problem. In the backward chain of reasoning, the system works backward from a question to produce an answer.

User Interface:

The user interface is the display screen that the user interacts with. If gives the user the ability to ask questions and get answers. It also explains the reasoning behind the answer.

Applications:

Expert systems exist in many areas.

MYCIN helps diagnose infections diseases. PROSPECTOR assesses geological data to locate mineral deposits. DENDRAL identifies chemical compounds. Home-Safe-Home evaluates the residential environment of an elderly Person. Business Insight helps businesses find the best strategies for marketing a Product REBES (Residential Burglary Expert System) helps dectives investigate Crime scenes. CARES (Computer Assisted Risk Evaluation System) help social workers Assess families for risks of child abuse. Muckraker assists journalists with investigate reporting.