Basic Knowledge of Computers

Classifications, generations, applications and limitations of digital computers

 

  • Computer Classification: By Size and Power

Computers differ based on their data processing abilities. They are classified according to purpose, data handling and functionality.

According to functionality, computers are classified as:

  • Analog Computer: A computer that represents numbers by some continuously variable physical quantity, whose variations mimic the properties of some system being modeled.
  • Personal computer: personal computeris a computer small and low cost. The term”personal computer” is used to describe desktop computers (desktops).
  • Workstation: A terminal or desktop computer in a network. In this context, workstation is just a generic term for a user’s machine (client machine) in contrast to a “server” or “mainframe.”
  • Minicomputer: minicomputer isn’t very mini. At least, not in the way most of us think of mini. You know how big the personal computer is and its related family.
  • Mainframe: It refers to the kind of large computer that runs an entire corporation.
  • Supercomputer: Itis the biggest, fastest, and most expensive computers on earth.
  • Microcomputer: A personal computer is a

According to purpose or functionality, computers are classified as general purpose and special purpose computers. General purpose computers solve large variety of problems.They are said to be multi purpose for they perform a wide range of tasks. Examples of general purpose computer include desktop and laptops.
On the other hand,special purpose computers solve only specific problems.They are dedicated to perform only particular tasks.Examples of special purpose computers can include calculators and money counting machine.

 

Generation of Digital Computers

According to age,computers are grouped in terms of generations. They include;1st generation computers,2nd generation computers,3rd generation computers,4th generation computers, and finally 5th generation.

1st  generation computers.This is a generation of computers that were discovered between the years 1946 and 1957.These computers had the following characteristics: They used vacuum tubes for circuiting.They used magnetic drums as memory for data processing.Their operating system was quite low as compared to the later generations.An operating system can be defined as a collection of programs designed to control the computer’s interaction and communication with the user. A computer must load the operating system like Microsoft into memory before it can load an application program like Ms Word.These computers required large space for installation.They were large in size and could take up the entire room.They consumed a lot of power.They also produced huge amounts of energy and power which saw machines breaking down oftenly. Using the computers,programming capabilities was quite low since the computers relied on machine language.Machine language can only be understood by the computer but not human beings .Their input was based on punched cards and paper tapes.

2nd  generation computers. These computers existed between the years 1958 and 1964.They possessed the following features:These computers used transistors for circuitry purposes.They were quite smaller in size compared to the 1st generation computers. Unlike the 1st generation computers, they consumed less power. Their operating system was faster.During this generation, programming languages such as COBOL and FORTRAN were developed.This phase of computers relied on punched cards too for input and printouts.

3rd generation computers.These are computers that existed between 1965 and 1971.The computers used integrated circuits(ICs) for circuitry purposes.The computers were smaller in size due to the introduction of the chip.They had a large memory for processing data. Their processing speed was much higher.The technology used in these computers was small scale integration (SSI) technology.

4th generation computers. The computers under this generation were discovered from 1972 to 1990s. The computers employed large scale integration (LSI) technology.The size of memory was /is high/large,hence faster processing of data.Their processing speed was high.The computers were also smaller in size and less costly in terms of installation.This phase of computers saw introduction of keyboards that could interface well with processing system.During this phase, there was rapid internet evolution.Other advances that were made included the introduction of GUI(graphical user interface) and mouses.Other than GUI, there exist other user interfaces like natural-language interface,question-and-answer interface,command line interface(CLI).

 

5th generation computers.These are computers that are still under development and invention. There development might have began in 1990s and continues in to the future. These computers use very large scale integration (VLSI) technology. The memory speed of these computers is extremely high.The computers can perform parallel processing. It is during this generation that Artificial Intelligence (AI) concept was generated e.g voice and speech recognition. These computers will use quantum computation and molecular technology.They will be able to interpret data and respond to it without direct control by human beings.

 

Applications and Limitations of Digital Computers

In a very general way, it can be said that the advantages of the digital computer compared to the analog computer,I are its greater flexibility and precision, while its disadvantages are its higher cost and complexity.

Information storage can be easier in digital computer systems than in analogue ones. New features can often be added to a digital system more easily too.

 

Computer-controlled digital systems can be controlled by software, allowing new functions to be added without changing hardware. Often this can be done outside of the factory by updating the product’s software. So, the product’s design errors can be corrected after the product is in a customer’s hands.

Information storage can be easier in digital systems than in analog ones. The noise-immunity of digital systems permits data to be stored and retrieved without degradation. In an analog system, noise from aging and wear degrade the information stored. In a digital system, as long as the total noise is below a certain level, the information can be recovered perfectly.

Digital computers play an important role in life today as they can be used to control industrial processes, analyse and organize business data, assist in scientific research and designing of automobiles and aircraf, and even help making special effects in movies. Some Main Applications of Digital Computers are as follows –

Recording Information

Official statistics keepers and some scouts use computers to record statistics, take notes and chat online while attending and working at a sports event.

Analyzing Movements

The best athletes pay close attention to detail. Computers can slow recorded video and allow people to study their specific movements to try to improve their tendencies and repair poor habits.

Writers

Many sportswriters attend several sporting events a week, and they take their computers with them to write during the game or shortly after while their thoughts are fresh in their mind.

 

The main disadvantages are that digital circuits use more energy than analogue circuits to accomplish the same tasks, thus producing more heat as well. Digital circuits are often fragile, in that if a single piece of digital data is lost or misinterpreted, the meaning of large blocks of related data can completely change.

 

 

Definition of digital computer, Elements of computer: Input unit, Output unit, Primary memory, Secondary memory and Processing unit.

 

 

  • Computer is an electronic device that is designed to work with Information. term computer is derived from the Latin termcomputare’, this means to calculateor programmable machineComputer cannot do anything without a Program. It represents the decimal numbers through a string of binary digits. The Word ‘Computer’ usually refers to the Center Processor Unit plus Internal memory.
  • Charles Babbageis called the “Grand Father” of the computer. The First mechanical computer designed by Charles Babbage was called Analytical Engine. It uses read-only memory in the form of punch cards.

 

Digital Computer Definition

 

  • The basic components of a modern digital computer are: Input Device, Output Device, Central Processor Unit (CPU), mass storage device and memory. A Typical modern computer uses LSI Chips.

 

Four Functions about computer are:

 

accepts dataInput
processes dataProcessing
produces outputOutput
stores resultsStorage

 

Input (Data):

Input is the raw information entered into a computer from the input devices. It is the collection of letters, numbers, images etc.

Process:

Process is the operation of data as per given instruction. It is totally internal process of the computer system.

Output:

Output is the processed data given by computer after data processing. Output is also called as Result. We can save these results in the storage devices for the future use.

 

All general-purpose computers require the following hardware components:

Memory: enables a computer to store, at least temporarily, data and programs.

Mass storage device: allows a computer to permanently retain large amounts of data. Common mass storage devices include solid state drives (SSDs) or disk drives and tape drives.

Input device: usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.

Output device: a display screen, printer, or other device that lets you see what the computer has accomplished.

Central processing unit (CPU): the heart of the computer, this is the component that actually executes instructions.

In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.

CPU (Processing Unit)

CPU (pronounced as separate letters) is the abbreviation for central processing unit. Sometimes referred to simply as the central processor, but more commonly called processor, the CPU is the brains of the computer where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system.

Components of a CPU

The two typical components of a CPU include the following:

The arithmetic logic unit (ALU), which performs arithmetic and logical operations.

The control unit (CU), which extracts instructions from memoryand decodes and executes them, calling on the ALU when necessary.

Relationship between the elements of the CPU, input and output, and storage

Printed Circuit Boards, Microprocessors

On large machines, the CPU requires one or more printed circuit boards. On personal computers and small workstations, the CPU is housed in a single chip called a microprocessor. Since the 1970’s the microprocessor class of CPUs has almost completely overtaken all other CPU implementations.

The CPU itself is an internal component of the computer. Modern CPUs are small and square and contain multiple metallic connectors or pins on the underside. The CPU is inserted directly into a CPU socket, pin side down, on the motherboard.

Each motherboard will support only a specific type (or range) of CPU, so you must check the motherboard manufacturer’s specifications before attempting to replace or upgrade a CPU in your computer. Modern CPUs also have an attached heat sink and small fan that go directly on top of the CPU to help dissipate heat.

 

 

MEMORY

 

Memory is major part of computers that categories into several types. Memory is best storage part to the computer users to save information, programs and etc, The computer memory offer several kinds of storage media some of them can store data temporarily and some them can store permanently. Memory consists of instructions and the data saved into computer through Central Processing Unit (CPU).

Types of Computer Memory:

Memory is the best essential element of a computer because computer can’t perform simple tasks. The performance of computer mainly based on memory and CPU. Memory is internal storage media of computer that has several names such as majorly categorized into two types, Main memory and Secondary memory.

 

  1. Primary Memory / Volatile Memory.
  2. Secondary Memory / Non Volatile Memory.

 

  1. Primary Memory / Volatile Memory:

 

Primary Memory also called as volatile memory because the memory can’t store the data permanently. Primary memory select any part of memory when user want to save the data in memory but that may not be store permanently on that location. It also has another name i.e. RAM.

Random Access Memory (RAM):

The primary storage is referred to as random access memory (RAM) due to the random selection of memory locations. It performs both read and write operations on memory. If power failures happened in systems during memory access then you will lose your data permanently. So, RAM is volatile memory. RAM categorized into following types.

DRAM

SRAM

DRDRAM

  1. Secondary Memory / Non Volatile Memory:

Secondary memory is external and permanent memory that is useful to store the external storage media such as floppy disk, magnetic disks, magnetic tapes and etc cache devices. Secondary memory deals with following types of components.

Read Only Memory (ROM) :

ROM is permanent memory location that offer huge types of standards to save data. But it work with read only operation. No data lose happen whenever power failure occur during the ROM memory work in computers.

ROM memory has several models such names are following.

  1. PROM:Programmable Read Only Memory (PROM) maintains large storage media but can’t offer the erase features in ROM. This type of RO maintains PROM chips to write data once and read many. The programs or instructions designed in PROM can’t be erased by other programs.
  2. EPROM :Erasable Programmable Read Only Memory designed for recover the problems of PROM and ROM. Users can delete the data of EPROM thorough pass on ultraviolet light and it erases chip is reprogrammed.
  3. EEPROM:Electrically Erasable Programmable Read Only Memory similar to the EPROM but it uses electrical beam for erase the data of ROM.

Cache Memory: Mina memory less than the access time of CPU so, the performance will decrease through less access time. Speed mismatch will decrease through maintain cache memory. Main memory can store huge amount of data but the cache memory normally kept small and low expensive cost. All types of external media like Magnetic disks, Magnetic drives and etc store in cache memory to provide quick access tools to the users.

 

 

Data, Data processing, business data processing, data storage, file management system and data base management systems.

 

Data, Data Processing and Database management System

 

Data processing and data management are critical components of business organizations.

 

DATA PROCESSING

Data processing refers to the process of performing specific operations on a set of data or a database. A database is an organized collection of facts and information, such as records on employees, inventory, customers, and potential customers. As these examples suggest, numerous forms of data processing exist and serve diverse applications in the business setting.

Data processing primarily is performed on information systems, a broad concept that encompasses computer systems and related devices. At its core, an information system consists of input, processing, and output. In addition, an information system provides for feedback from output to input. The input mechanism (such as a keyboard, scanner, microphone, or camera) gathers and captures raw data and can be either manual or automated. Processing, which also can be accomplished manually or automatically, involves transforming the data into useful outputs. This can involve making comparisons, taking alternative actions, and storing data for future use. Output typically takes the form of reports and documents that are used by managers. Feedback is utilized to make necessary adjustments to the input and processing stages of the information system.

The processing stage is where management typically exerts the greatest control over data. It also is the point at which management can derive the most value from data, assuming that powerful processing tools are available to obtain the intended results. The most frequent processing procedures available to management are basic activities such as segregating numbers into relevant groups, aggregating them, taking ratios, plotting, and making tables. The goal of these processing activities is to turn a vast collection of facts into meaningful nuggets of information that can then be used for informed decision making, corporate strategy, and other managerial functions.

DATA  AND INFORMATION

Data consist of raw facts, such as customer names and addresses. Information is a collection of facts organized in such a way that it has more value beyond the facts themselves. For example, a database of customer names and purchases might provide information on a company’s market demographics, sales trends, and customer loyalty/turnover.

Turning data into information is a process or a set of logically related tasks performed to achieve a defined outcome. This process of defining relationships between various data requires knowledge. Knowledge is the body or rules, guidelines, and procedures used to select, organize, and manipulate data to make it suitable for specific tasks. Consequently, information can be considered data made more useful through the application of knowledge. The collection of data, rules, procedures, and relationships that must be followed are contained in the knowledge base.

CHARACTERISTICS OF VALUABLE INFORMATION.

In order for information to be valuable it must have the following characteristics, as adapted from Ralph M. Stair’s book, Principles of Information Systems:

  1. Accurate. Accurate information is free from error.
  2. Complete. Complete information contains all of the important facts.
  3. Economical. Information should be relatively inexpensive to produce.
  4. Flexible. Flexible information can be used for a variety of purposes, not just one.
  5. Reliable. Reliable information is dependable information.
  6. Relevant. Relevant information is important to the decision-maker.
  7. Simple. Information should be simple to find and understand.
  8. Timely. Timely information is readily available when needed.
  9. Verifiable. Verifiable information can be checked to make sure it is accurate.

DATA MANAGEMENT

Data are organized in a hierarchy that begins with the smallest piece of data used by a computer—for purposes of this discussion, a single character such as a letter or number. Characters form fields such as names, telephone numbers, addresses, and purchases. A collection of fields makes up a record. A collection of records is referred to as a file. Integrated and related files make up a database.

An entity is a class of people, objects, or places for which data are stored or collected. Examples include employees and customers. Consequently, data are stored as entities, such as an employee database and a customer database. An attribute is a characteristic of an entity. For example, the name of a customer is an attribute of a customer. A specific value of an attribute is referred to as a data item. That is, data items are found in fields.

The traditional approach to data management consists of maintaining separate data files for each application. For example, an employee file would be maintained for payroll purposes, while an additional employee file might be maintained for newsletter purposes. One or more data files are created for each application. However, duplicated files results in data redundancy. The problem with data redundancy is the possibility that updates are accomplished in one file but not in another, resulting in a lack of data integrity. Likewise, maintaining separate files is generally inefficient because the work of updating and managing the files is duplicated for each separate file that exists. To overcome potential problems with traditional data management, the database approach was developed.

The database approach is such that multiple business applications access the same database. Consequently, file updates are not required of multiple files. Updates can be accomplished in the common database, thus improving data integrity and eliminating redundancy. The database approach provides the opportunity to share data, as well as information sources. Additional software is required to implement the database approach to data management. A database management system (DBMS) is needed. A DBMS consists of a group of programs that are used in an interface between a database and the user, or between the database and the application program.

DATA ORGANIZATION.

Data organization is critical to optimal data use. Consequently, it is important to organize data in such a manner as to reflect business operations and practices. As such, careful consideration should be given to content, access, logical structure, and physical organization. Content refers to what data are going to be collected. Access refers to the users that data are provided to when appropriate. Logical structure refers to how the data will be arranged. Physical structure refers to where the data will be located.

One tool that database designers use to show the logical relationships among data is a data model, which is a map or diagram of entities and their relationships. Consequently, data modeling requires a thorough understanding of business practices and what kind of data and information is needed.

DATABASE MODELS.

The structure of the relationships in most databases follows one of three logical database models: hierarchical, network, and relational.

A hierarchical database model is one in which the data are organized in a top-down or inverted tree-like structure. This type of model is best suited for situations where the logical relationships between data can be properly represented with the one-parent-many-children approach.

A network model is an extension of the hierarchical database model. The network model has an owner-member relationship in which a member may have many owners, in contrast to a one-to-many-relationship.

A relational model describes data using a standard tabular format. All data elements are placed in two-dimensional tables called relations, which are the equivalent of files. Data inquiries and manipulations can be made via columns or rows given specific criteria.

Network database models tend to offer more flexibility than hierarchical models. However, they are more difficult to develop and use because of relationship complexity. The relational database model offers the most flexibility, and was very popular during the early 2000s.

 

DATABASE MANAGEMENT SYSTEMS.

As indicated previously, a database management system (DBMS) is a group of programs used as an interface between a database and an applications program. DBMSs are classified by the type of database model they support. A relational DBMS would follow the relational model, for example. The functions of a DBMS include data storage and retrieval, database modifications, data manipulation, and report generation.

A data definition language (DDL) is a collection of instructions and commands used to define and describe data and data relationships in a particular database. File descriptions, area descriptions, record descriptions, and set descriptions are terms the DDL defines and uses.

A data dictionary also is important to database management. This is a detailed description of the structure and intended content in the database. For example, a data dictionary might specify the maximum number of characters allowed in each type of field and whether the field content can include numbers, letters, or specially formatted content such as dates or currencies. Data dictionaries are used to provide a standard definition of terms and data elements, assist programmers in designing and writing programs, simplify database modifications, reduce data redundancy,increase data reliability, and decrease program development time.

The choice of a particular DBMS typically is a function of several considerations. Economic cost considerations include software acquisition costs, maintenance costs, hardware acquisition costs, database creation and conversion costs, personnel costs, training costs, and operating costs.

Most DBMS vendors are combining their products with text editors and browsers, report generators, listing utilities, communication software, data entry and display features, and graphical design tools. Consequently, those looking for a total design system have many choices.

DATA WAREHOUSING.

Data warehousing involves taking data from a main computer for analysis without slowing down the main computer. In this manner, data are stored in another database for analyzing trends and new relationships. Consequently, the data warehouse is not the live, active system, but it is updated daily or weekly. For example, Wal-Mart uses a very large database (VLDB) that is 4 trillion bytes (terabytes) in size. Smaller parts of this database could be warehoused for further analysis to avoid slowing down the VLDB.

FUTURE TRENDS and BUSINESS DATA PROCESSING

A private database is compiled from individual consumer or business customer names and addresses maintained by a company for use in its own marketing efforts. Such a database may have originated as a public database, but typically once the company begins adding or removing information it is considered a private database. By contrast, public databases are those names, addresses, and data that are complied for resale in the list rental market. This is publicly available data (i.e., any business can purchase it on the open market) rather than lists of specific customers or targets.

However, a new trend is combining features of the two approaches. Cooperative databases are compiled by combining privately held response files of participating companies so that costs are shared. Many consider this to be a future trend, such that virtually all catalog marketers, for example, would use cooperative databases.

Geographic Information Systems (GIS) are becoming a growing area of data management. GIS involves the combining demographic, environmental, or other business data with geographic data. This can involve road networks and urban mapping, as well as consumer buying habits and how they relate to the local geography. Output is often presented in a visual data map that facilitates the discovery of new patterns and knowledge.

Customer Resource Management (CRM) is another area where data process and data management is deeply involved. CRM is a set of methodologies and software applications for managing the customer relationship. CRM provides the opportunity for management, salespeople, marketers, and potentially even customers, to see sufficient detail regarding customer activities and contacts. This allows companies to provide other possible products or useful services, as well as other business options. Security of this information is of significant concern on both sides of the equation.
File Management System

Also referred to as simply a file system or filesystem. The system that an operating system or program uses to organize and keep track of files. For example, a hierarchical file system is one that uses directories to organize files into a tree structure.

Although the operating system provides its own file management system, one can buy separate file management systems. These systems interact smoothly with the operating system but provide more features, such as improved backup proceduresand stricter file protection.

 

 

 

Definition of Internet, search tools, web browsers, e-mail and search engines. IT applications: E-cards, E- shopping, E-commerce.

 

  • INTERNET

 

  • The Internet is a global network of billions of computers and other electronic devices. With the Internet, it’s possible to access almost any information, communicate with anyone else in the world, and do much more.
  • It’s important to realize that the Internet is a global network of physical cables, which can include copper telephone wires, TV cables, and fiber optic cables. Even wireless connections like Wi-Fi and 3G/4G rely on these physical cables to access the Internet.

 

  • On visiting a website, the computer sends a request over these wires to a server. A server is where websites are stored, and it works a lot like computer’s hard drive. Once the request arrives, the server retrieves the website and sends the correct data back to computer.

 

  • The World Wide Web—usually called the Webfor short—is a collection of different websites you can access through the Internet. A website is made up of related text, images, and other resources. Websites can resemble other forms of media—like newspaper articles or television programs—or they can be interactive in a way that’s unique to computers.
  • The purpose of a website can be almost anything: a news platform, an advertisement, an online library, a forum for sharing images, or an educational site.
  • WEB BROWSER
  • Web Browseris an application software that allows us to view and explore information on the web. In other words, a browser is a software program created as a simplified means to present and explore content on the World Wide Web. These pieces of content, including pictures, videos, and web pages, are connected using hyperlinks and classified with Uniform Recourse Identifiers (URLs).

 

  • There have been many different web browsers that have come and gone over the years. The first, named WorldWideWeb (later changed to Nexus), was invented by Tim Berners-Leein 1990. However, the first graphical browser and widely used browser that help bring popularity to the Internet was NCSA Mosaic.

 

  • List of current Internet browsers
BrowserVendor
Internet ExplorerMicrosoft
Google ChromeGoogle
Mozilla FirefoxMozilla
Netscape NavigatorNetscape Communications Corp.
OperaOpera Software
SafariApple
Sea MonkeyMozilla Foundation
K-meleonK-meleon

 

·                  Email

  • Email is a service which allows us to send the message in electronic mode over the internet. It offers an efficient, inexpensive and real time mean of distributing information among people.

E-Mail Address

  • Each user of email is assigned a unique name for his email account. This name is known as E-mail address. Different users can send and receive messages according to the e-mail address.
  • E-mail is generally of the form username@domainname. For example, webmaster@tutorialspoint.com is an e-mail address where webmaster is username and tutorialspoint.com is domain name.
  • The username and the domain name are separated by @ (at)
  • E-mail addresses are not case sensitive.
  • Spaces are not allowed in e-mail address.

E-mail Message Components

 

  • E-mail message comprises of different components: E-mail Header, Greeting, Text, and Signature.

         E-mail Header

 

  • The first five lines of an E-mail message is called E-mail header. The header part comprises of following fields:
  • From
  • Date
  • To
  • Subject
  • CC
  • BCC

FROM

The From field indicates the sender’s address i.e. who sent the e-mail.

DATE

The Date field indicates the date when the e-mail was sent.

TO

The To field indicates the recipient’s address i.e. to whom the e-mail is sent.

SUBJECT

The Subject field indicates the purpose of e-mail. It should be precise and to the point.

CC

CC stands for Carbon copy. It includes those recipient addresses whom we want to keep informed but not exactly the intended recipient.

BCC

BCC stands for Black Carbon Copy. It is used when we do not want one or more of the recipients to know that someone else was copied on the message.

Greeting

Greeting is the opening of the actual message. Eg. Hi Sir or Hi Guys etc.

Text

It represents the actual content of the message.

Signature

This is the final part of an e-mail message. It includes Name of Sender, Address, and Contact Number.

E-mail System

 

E-mail system comprises of the following three components:

  • Mailer
  • Mail Server
  • Mailbox

Mailer

It is also called mail program, mail application or mail client. It allows us to manage, read and compose e-mail.

Mail Server

The function of mail server is to receive, store and deliver the email. It is must for mail servers to be sunning all the time because if it crashes or is down, email can be lost.

Mailboxes

Mailbox is generally a folder that contains emails and information about them.

 

E-mail Protocols are set of rules that help the client to properly transmit the information to or from the mail server. Here in this tutorial, we will discuss various protocols such as SMTP, POP, and IMAP.

SMPTP

SMTP stands for Simple Mail Transfer Protocol. It was first proposed in 1982. It is a standard protocol used for sending e-mail efficiently and reliably over the internet.

Key Points:

  • SMTP is application level protocol.
  • SMTP is connection oriented protocol.
  • SMTP is text based protocol.
  • It handles exchange of messages between e-mail servers over TCP/IP network.
  • Apart from transferring e-mail, SMPT also provides notification regarding incoming mail.
  • When you send e-mail, your e-mail client sends it to your e-mail server which further contacts the recipient mail server using SMTP client.
  • These SMTP commands specify the sender’s and receiver’s e-mail address, along with the message to be send.
  • The exchange of commands between servers is carried out without intervention of any user.
  • In case, message cannot be delivered, an error report is sent to the sender which makes SMTP a reliable protocol.

IMAP

IMAP stands for Internet Mail Access Protocol. It was first proposed in 1986. There exist five versions of IMAP as follows:

  1. Original IMAP
  2. IMAP2
  3. IMAP3
  4. IMAP2bis
  5. IMAP4

Key Points:

  • IMAP allows the client program to manipulate the e-mail message on the server without downloading them on the local computer.
  • The e-mail is hold and maintained by the remote server.
  • It enables us to take any action such as downloading, delete the mail without reading the mail.It enables us to create, manipulate and delete remote message folders called mail boxes.
  • IMAP enables the users to search the e-mails.
  • It allows concurrent access to multiple mailboxes on multiple mail servers.

POP

POP stands for Post Office Protocol. It is generally used to support a single client. There are several versions of POP but the POP 3 is the current standard.

Key Points

  • POP is an application layer internet standard protocol.
  • Since POP supports offline access to the messages, thus requires less internet usage time.
  • POP does not allow search facility.
  • In order to access the messaged, it is necessary to download them.
  • It allows only one mailbox to be created on server.
  • It is not suitable for accessing non mail data.
  • POP commands are generally abbreviated into codes of three or four letters. Eg. STAT.
  • Comparison between POP and IMAP
S.N.POPIMAP
1Generally used to support single client.Designed to handle multiple clients.
2Messages are accessed offline.Messages are accessed online although it also supports offline mode.
3POP does not allow search facility.It offers ability to search emails.
4All the messages have to be downloaded.It allows selective transfer of messages to the client.
5Only one mailbox can be created on the server.Multiple mailboxes can be created on the server.
6Not suitable for accessing non-mail data.Suitable for accessing non-mail data i.e. attachment.
7POP commands are generally abbreviated into codes of three or four letters. Eg. STAT.IMAP commands are not abbreviated, they are full. Eg. STATUS.
8It requires minimum use of server resources.Clients are totally dependent on server.
9Mails once downloaded cannot be accessed from some other location.Allows mails to be accessed from multiple locations.
10The e-mails are not downloaded automatically.Users can view the headings and sender of e-mails and then decide to download.
10POP requires less internet usage time.IMAP requires more internet usage time.

 

 

  • Search Engine and Search Tools

 

Search Engine refers to a huge database of internet resources such as web pages, newsgroups, programs, images etc. It helps to locate information on World Wide Web.

User can search for any information by passing query in form of keywords or phrase. It then searches for relevant information in its database and return to the user.

Search Engine Components

Generally there are three basic components of a search engine as listed below:

  1. Web Crawler
  2. Database
  3. Search Interfaces

Web crawler

It is also known as spider or bots. It is a software component that traverses the web to gather information.

Database

All the information on the web is stored in database. It consists of huge web resources.

Search Interfaces

This component is an interface between user and the database. It helps the user to search through the database.

 

Search Engine Working

Web crawler, database and the search interface are the major component of a search engine that actually makes search engine to work. Search engines make use of Boolean expression AND, OR, NOT to restrict and widen the results of a search. Following are the steps that are performed by the search engine:

  • The search engine looks for the keyword in the index for predefined database instead of going directly to the web to search for the keyword.
  • It then uses software to search for the information in the database. This software component is known as web crawler.
  • Once web crawler finds the pages, the search engine then shows the relevant web pages as a result. These retrieved web pages generally include title of page, size of text portion, first several sentences etc.

These search criteria may vary from one search engine to the other. The retrieved information is ranked according to various factors such as frequency of keywords, relevancy of information, links etc.

  • User can click on any of the search results to open it.

 

Search Engine Processing

Indexing Process

Indexing process comprises of the following three tasks:

  • Text acquisition
  • Text transformation
  • Index creation

Text Acquisition

It identifies and stores documents for indexing.

Text Transformation

It transforms document into index terms or features.

Index Creation

It takes index terms created by text transformations and create data structures to support fast searching.

Query Process

Query process comprises of the following three tasks:

  • User interaction
  • Ranking
  • Evaluation

User Interaction

It supporst creation and refinement of user query and displays the results.

Ranking

It uses query and indexes to create ranked list of documents.

Evaluation

It monitors and measures the effectiveness and efficiency. It is done offline.

Examples

Following are the several search engines available today:

Search EngineDescription
GoogleIt was originally called BackRub. It is the most popular search engine globally.
BingIt was launched in 2009 by Microsoft. It is the latest web-based search engine that also delivers Yahoo’s results.
AskIt was launched in 1996 and was originally known as Ask Jeeves. It includes support for match, dictionary, and conversation question.
AltaVistaIt was launched by Digital Equipment Corporation in 1995. Since 2003, it is powered by Yahoo technology.
AOL.SearchIt is powered by Google.
LYCOSIt is top 5 internet portal and 13th largest online property according to Media Matrix.
AlexaIt is subsidiary of Amazon and used for providing website traffic information.

 

Search Tools

There are three basic types of search tools that most people use to find what they are looking for on the Web.

  • Search Engines
  • Subject Directories
  • Meta Search Tools

None of these search tools allow  to search the entire Web; that would be an almost impossible task. However, one can use these Web search tools to scour different parts of the Web, obtain different types of information, and broaden the Web search horizons.

Search the Web with Search Engines

Search engines are large, spider(software programs) created databases of web pages that help searchers find specific information on any given subject. When anyone  type in a keyword or phrase and the search engine retrieves pages that correspond to the search query.

Search results gathered from these search engines are not always relevant to the keywords entered since these engines are not intuitive and cannot infer dynamically what it is, one might be searching for (although results are getting better all the time). This is why it’s important to learn how to search as efficiently as possible using such techniques as Boolean search, or basic Google search techniques.

 

Interpretation of relevancy is different in each search engine. Many search engineshave included categories to direct users to more relevant sites based on these particular topics.

Search the Web with Subject Directories

Subject directories, in general, are smaller and selective that search engines. They use categories to focus the search, and their sites are arranged by categories, not just by keywords. Subject directories are handy for broad searches, as well as finding specific websites. Most subject directories’ main purpose is to be informational, rather than commercial. A good example of a search directory is Yahoo, a combination search engine/search directory/search portal, or one of the original search directories, Open Directory or DMOZ for short.

Search the Web with Metasearch Engines

Metasearch engines get their search results from several search engines. Users will receive the best hits to their keywords from each search engine. Metasearch tools are a good place to start for very broad results but do not (usually) give the same quality results as using each search engine and directory.

 

 

  • IT applications- E-Cards, E-Shopping, E-Commerce

E-Cards

An electronic card (e-card) is a special occasion, greeting or post card created and customized within a website and sent through the Internet to the recipient. Customizations may include a wide variety of backgrounds and text fonts including some as cursive writing, graphic images, cartoon-style animations (proprietary to Adobe), video and sometimes even music.

This term is also known as ecard, icard, i-card, digital postcard, cyber greeting card or digital greeting card.

Virtual cards were first started by Judith Donath at MIT Media Lab in 1994 and were created by the website called The Electronic Postcard.

Virtual card recipients are often sent an email with a link to a website where the card was created. Then the card may be viewed, played, copied, printed, etc. Such websites invariably include banner ads and others selling a variety of products. Some websites use virtual cards to market and draw attention to their other products and services, which may be their main product or service. The recipient is offered the opportunity to send their own customized cards to friends, family, etc. using their desktop machines, mobile devices and phones.

Advantages of virtual cards include the ease of sending them to many recipients, being environmentally friendly compared to paper/hard copy cards and the versatile and highly customizable content.

E-Shopping

When you buy a product or a service over the internet, instead of going to a traditional brick-and-mortar store, it is called online shopping. Globally, an increasing number of people are buying over the Internet because it is more convenient.
Online Products
starting with groceries and greeting cards to cell phones and ringtones for the cell phones, everything can be purchased online. While most people still find it convenient to buy their groceries from the neighbourhood shop, many people are purchasing rail and air tickets over the Internet. In addition, people and corporates as well, are also purchasing a variety of services online — such as a broking service or job search service.
Brief History

Online shopping became popular during the Internet boom in 1999-2000. Amazon.com, the online bookstore founded by Jeff Bezos, created history by becoming the first bookstore with a presence only on the Internet. Following the success of Amazon, many bookstores with a physical presence also created an online presence on the Internet. Later, portals such as Yahoo.com and MSN.com also started online shopping channels where people could buy more than just books. Closer home, portals such as Indiatimes.com and Rediff.com came up with similar options for the Indian consumer.
Advantages of shopping online

It is convenient, faster and sometimes also cheaper. For instance, rather than standing in a long queue and waiting for your turn to purchase a ticket, people are finding it simpler to log on to a website and buy it. In some instances, one may have to pay a premium for an online purchase but it is still preferred because the convenience factor is higher.
Payment

 

Although online players in India are coming up with innovative ways to make payments, credit cards are still the most widely accepted form of making payments over the Internet.
Security of payment

Security standards for online shopping are now well-established, so it is safe to pay online using your credit card. Your credit card details and other information are encrypted and sent over a secure layer over the Internet. Although no system is completely fraud-proof, the large number of people going online bears testimony to the acceptance and safety of online shopping.
Future scope

 

Now a days, with more advanced technologies many things are about to come. Cheap internet and Mobile with widely avilable services as well as incresing Mobile apps, giving huge boost to online shopping. With Digital India Scheme and technology development, online shopping has been spread very fast in India.

 

E Commerce

E-commerce is a transaction of buying or selling online. Electronic commerce draws on technologies such as mobile commerce, electronic funds transfer, supply chain management, Internet marketing, online transaction processing, electronic data interchange (EDI), inventory management systems, and automated data collection systems.

Examples of Ecommerce

·         Online Shopping

Buying and selling goods on the Internet is one of the most popular examples of ecommerce. Sellers create storefronts that are the online equivalents of retail outlets. Buyers browse and purchase products with mouse clicks. Though Amazon.com is not the pioneer of online shopping, it is arguably the most famous online shopping destination.

·         Electronic Payments

When you are buying goods online, there needs to be a mechanism to pay online too. That is where payment processors and payment gateways come into the picture.

Electronic payments reduce the inefficiency associated with writing and mailing checks. It also does away with many of the safety issues that arise due to payment made in currency notes.

·         Online Auctions

When you think online auction, you think eBay. Physical auctions predate online auctions, but the Internet made auctions accessible to a large number of buyers and sellers. Online auctions are an efficient mechanism for price discovery. Many buyers find the auction shopping mechanism much interesting than regular storefront shopping.

·         Internet Banking

Today it is possible for you to perform the entire gamut of banking operations without visiting a physical bank branch. Interfacing of websites with bank accounts, and by extension credit cards, was the biggest driver of ecommerce.

·         Online Ticketing

Air tickets, movie tickets, train tickets, play tickets, tickets to sporting events, and just about any kind of tickets can be booked online. Online ticketing does away with the need to queue up at ticket counters.

Types of Ecommerce

Ecommerce can be classified based on the type of participants in the transaction:

·         Business to Business (B2B)

B2B ecommerce transactions are those where both the transacting parties are businesses, e.g., manufacturers, traders, retailers and the like.

·         Business to Consumer (B2C)

When businesses sell electronically to end-consumers, it is called B2C ecommerce.

·         Consumer to Consumer (C2C)

Some of the earliest transactions in the global economic system involved barter — a type of C2C transaction. But C2C transactions were virtually non-existent in recent times until the advent of ecommerce. Auction sites are a good example of C2C ecommerce.

Benefits of Ecommerce

The primary benefits of ecommerce revolve around the fact that it eliminates limitations of time and geographical distance. In the process, ecommerce usually streamlines operations and lowers costs.

Specialized Forms of Ecommerce

On some platforms, ecommerce has shown the promise of explosive growth. Two such examples are:

·         M Commerce

Mcommerce is short for “mobile commerce.” The rapid penetration of mobile devices with Internet access has opened new avenues of ecommerce for retailers.

·         F Commerce

Fcommerce is short for “Facebook commerce.” The immense popularity of Facebook provides a captive audience to transact business.

Basic element of Communication systems, data transmission mode, transmission media, network topologies, network types, communication protocols, network security mechanism.

 

 

  • Elements of a Communication System

Elements of a communication system

The above figure depicts the elements of a communication system. There are three essential parts of any communication system, the transmitter, transmission channel, and receiver. Each parts plays a particular role in signal transmission, as follows:

The transmitter processes the input signal to produce a suitable transmitted signal suited to the characteristics of the transmission channel.

Signal processing for transmissions almost always involves modulation and may also include coding.

The transmission channel is the electrical medium that bridges the distance from source to destination. It may be a pair of wires, a coaxial cable, or a radio wave or laser beam. Every channel introduces some amount of transmission loss or attenuation. So, the signal power progressively decreases with increasing distance.

The receiver operates on the output signal from the channel in preparation for delivery to the transducer at the destination. Receiver operations include amplification to compensate for transmission loss. These also include demodulation and decoding to reverse the signal procession performed at the transmitter. Filtering is another important function at the receiver.

The figure represents one-way or simplex (SX) transmission. Two way communication of course requires a transmitter and receiver at each end. A full-duplex (FDX) system has a channel that allows simultaneous transmission in both directions. A half-duplex (HDX) system allows transmission in either direction but not at the same time.

  • Transmission Modes in Computer Networks

Transmission mode means transferring of data between two devices. It is also called communication mode. These modes direct the direction of flow of information. There are three types of transmission mode. They are :

Simplex Mode

Half duplex Mode

Full duplex Mode

SIMPLEX Mode

In this type of transmission mode data can be sent only through one direction i.e. communication is unidirectional. We cannot send a message back to the sender. Unidirectional communication is done in Simplex Systems.

Examples of simplex Mode is loudspeaker, television broadcasting, television and remote, keyboard and monitor etc.

 

HALF DUPLEX Mode

In half duplex system we can send data in both directions but it is done one at a time that is when the sender is sending the data then at that time we can’t send the sender our message. The data is sent in one direction.

Example of half duplex is a walkie- talkie in which message is sent one at a time and messages are sent in both the directions.

 

FULL DUPLEX Mode

In full duplex system we can send data in both directions as it is bidirectional. Data can be sent in both directions simultaneously. We can send as well as we receive the data.

Example of Full Duplex is a Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time.

In full duplex system there can be two lines one for sending the data and the other for receiving data.

 

 

  • TRANSMISSION MEDIA

Factors to be considered while choosing Transmission Medium

Transmission Rate

Cost and Ease of Installation

Resistance to Environmental Conditions

Distances

 

 

Coaxial Cable

Coaxial is called by this name because it contains two conductors that are parallel to each other. Copper is used in this as centre conductor which can be a solid wire or a standard one. It is surrounded by PVC installation, a sheath which is encased in an outer conductor of metal foil, barid or both.

Outer metallic wrapping is used as a shield against noise and as the second conductor which completes the circuit. The outer conductor is also encased in an insulating sheath. The outermost part is the plastic cover which protects the whole cable

Fiber Optic Cable

These are similar to coaxial cable. It uses electric signals to transmit data. At the centre is the glass core through which light propagates.

In multimode fibres, the core is 50microns, and In single mode fibres, the thickness is 8 to 10 microns.

The core in fiber optic cable is surrounded by glass cladding with lower index of refraction as compared to core to keep all the light in core. This is covered with a thin plastic jacket to protect the cladding. The fibers are grouped together in bundles protected by an outer shield.

Fiber optic cable has bandwidth more than 2 gbps (Gigabytes per Second)

Unguided or wireless media sends the data through air (or water), which is available to anyone who has a device capable of receiving them. Types of unguided/ unbounded media are discussed below :

Radio Transmission

MicroWave Transmission

 

Radio Transmission

Its frequency is between 10 kHz to 1GHz. It is simple to install and has high attenuation. These waves are used for multicast communications.

Types of Propogation

Radio Transmission utilizes different types of propogation :

  • Troposphere : The lowest portion of earth’s atmosphere extending outward approximately 30 miles from the earth’s surface. Clouds, jet planes, wind is found here.
  • Ionosphere : The layer of the atmosphere above troposphere, but below space. Contains electrically charged particles.

Microwave Transmission

It travels at high frequency than the radio waves. It requires the sender to be inside of the receiver. It operates in a system with a low gigahertz range. It is mostly used for unicast communication.

There are 2 types of Microwave Transmission :

  1. Terrestrial Microwave
  2. Satellite Microwave

Terrestrial Microwave

For increasing the distance served by terrestrial microwave, repeaters can be installed with each antenna .The signal received by an antenna can be converted into transmittable form and relayed to next antenna as shown in below figure. It is an example of telephone systems all over the world

 

Satellite Microwave

This is a microwave relay station which is placed in outer space. The satellites are launched either by rockets or space shuttles carry them.

These are positioned 36000KM above the equator with an orbit speed that exactly matches the rotation speed of the earth. As the satellite is positioned in a geo-synchronous orbit, it is stationery relative to earth and always stays over the same point on the ground. This is usually done to allow ground stations to aim antenna at a fixed point in the sky.

 

 

NETWORK TOPOLOGIES

Network Topology refers to the layout of a network and how different nodes in a network are connected to each other and how they communicate. Topologies are either physical (the physical layout of devices on a network) or logical (the way that the signals act on the network media, or the way that the data passes through the network from one device to the next).

Mesh Topology

 In a mesh network, devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network. There are two types of mesh topologies:

Full mesh topology: occurs when every node has a circuit connecting it to every other node in a network. Full mesh is very expensive to implement but yields the greatest amount of redundancy, so in the event that one of those nodes fails, network traffic can be directed to any of the other nodes. Full mesh is usually reserved for backbone networks.

Partial mesh topology: is less expensive to implement and yields less redundancy than full mesh topology. With partial mesh, some nodes are organized in a full mesh scheme but others are only connected to one or two in the network. Partial mesh topology is commonly found in peripheral networks connected to a full meshed backbone.

2. Star Topology

In a star network devices are connected to a central computer, called a hub. Nodes communicate across the network by passing data through the hub.

 Main Advantage: In a star network, one malfunctioning node doesn’t affect the rest of the network.
Main Disadvantage: If the central computer fails, the entire network becomes unusable.

3. Bus Topology

In networking a bus is the central cable — the main wire — that connects all devices on a local-area network (LAN). It is also called the backbone. This is often used to describe the main network connections composing the Internet.  Bus networks are relatively inexpensive and easy to install for small networks. Ethernet systems use a bus topology.

Main Advantage:  It’s easy to connect a computer or device and typically it requires less cable than a star topology.
Main Disadvantage: The entire network shuts down if there is a break in the main wire and it can be difficult to identify the problem if the network shuts down.

4. Ring Topology

Ring Topology: A local-area network (LAN) whose topology is a ring. That is, all of the nodes are connected in a closed loop. Messages travel around the ring, with each node reading those messages addressed to it.
Main Advantage: One main advantage to a ring network is that it can span larger distances than other types of networks, such as bus networks, because each node regenerates messages as they pass through it.

 

  1. Tree Topology

This is a “hybrid” topology that combines characteristics of linear bus and star topologies. In a tree network, groups of star-configured networks are connected to a linear bus backbone cable.

Main Advantage: A Tree topology is a good choice for large computer networks as the tree topology “divides” the whole network into parts that are more easily manageable.
Main Disadvantage: The entire network depends on a central hub and a failure of the central hub can cripple the whole network.

·        NETWORK TYPES

 

 

Local Area Network (LAN)

It is also called LAN and designed for small physical areas such as an office, group of buildings or a factory. LANs are used widely as it is easy to design and to troubleshoot. Personal computers and workstations are connected to each other through LANs. We can use different types of topologies through LAN, these are Star, Ring, Bus, Tree etc.

LAN can be a simple network like connecting two computers, to share files and network among each other while it can also be as complex as interconnecting an entire building.

LAN networks are also widely used to share resources like printers, shared hard-drive etc.

Applications of LAN

One of the computer in a network can become a server serving all the remaining computers called clients. Software can be stored on the server and it can be used by the remaining clients.

Connecting Locally all the workstations in a building to let them communicate with each other locally without any internet access.

Sharing common resources like printers etc are some common applications of LAN.

Metropolitan Area Network (MAN)

It is basically a bigger version of LAN. It is also called MAN and uses the similar technology as LAN. It is designed to extend over the entire city. It can be means to connecting a number of LANs into a larger network or it can be a single cable. It is mainly hold and operated by single private company or a public company.

 

Wide Area Network (WAN)

It is also called WAN. WAN can be private or it can be public leased network. It is used for the network that covers large distance such as cover states of a country. It is not easy to design and maintain. Communication medium used by WAN are PSTN or Satellite links. WAN operates on low data rates.

 

Wireless Network

It is the fastest growing segment of computer. They are becoming very important in our daily life because wind connections are not possible in cars or aeroplane. We can access Internet at any place avoiding wire related troubles.. These can be used also when the telephone systems gets destroyed due to some calamity/disaster. WANs are really important now-a-days.

 

Inter Network

When we connect two or more networks then they are called internetwork or internet. We can join two or more individual networks to form an internetwork through devices like routers gateways or bridges.

 

·        COMMUNICATION PROTOCOL

Communication protocols are formal descriptions of digital message formats and rules. They are required to exchange messages in or between computing systems and are required in telecommunications.

Communications protocols cover authentication, error detection and correction, and signaling. They can also describe the syntax, semantics, and synchronization of analog and digital communications. Communications protocols are implemented in hardware and software. There are thousands of communications protocols that are used everywhere in analog and digital communications. Computer networks cannot exist without them.

Communications devices have to agree on many physical aspects of the data to be exchanged before successful transmission can take place. Rules defining transmissions are called protocols.

There are many properties of a transmission that a protocol can define. Common ones include: packet size, transmission speed, error correction types, handshaking and synchronization techniques, address mapping, acknowledgement processes, flow control, packet sequence controls, routing, and address formatting

Popular protocols include: File Transfer Protocol (FTP), TCP/IP, User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), Post Office Protocol (POP3), Internet Message Access Protocol (IMAP), Simple Mail Transfer Protocol (SMTP).

Application Layer Protocol – HTTP and IRC

HTTP

The HyperText Transfer Protocol (HTTP) is the most common protocol in use on the internet. The protocol’s job is to transfer HyperText (such as HTML) from a server to computer. HTTP functions as a simple conversation between client and server.

IRC

Internet Relay Chat (IRC) is a system that lets someone to transfer messages in the form of text. It’s essentially a chat protocol. The system uses a client-server model. Clients are chat programs installed on a user’s computer that connect to a central server. The clients communicate the message to the central server which in turn relays that to other clients. The protocol was originally designed for group communication in a discussion forum, called channels. IRC also supports one-to-one communication via private messages. It is also capable of file and data transfer too.

Transport Layer Protocol – TCP/IP

TCP (The Transmission Control Protocol) is one of the most important protocols on the internet. It breaks large messages up into packets.

During the late 1970’s and into the 80’s, the U.S. Department of Defense experienced numerous technical failures when attempting to connect multiple computers (nodes) and multiple networks with the intent of sharing data and information. In 1981, the government was successful following the implementation of the Transmission Control Protocol (TCP) and the Internet Protocol (IP) technologies. in bringing the Internet alive with these combined (TCP/IP) technologies, project engineers and researchers were able to meet the needs of most users by enabling online capabilities to perform file transfers, e-mail, file sharing and remote log on functions.

IP : The Internet Protocol is responsible for moving data, in the form of electronic packets, along the internet network until the packets are received at the intended destination or IP address.

TCP: The Transmission Control Protocol is responsible for ensuring safe delivery of each data packet from the sending node to the receiving node within a network. In addition, because data packets can be misdirected or damaged during transmission, the TCP detects these errors as they occur during the transmission and automatically retransmits each questionable data packet.

As the Internet’s protocol suite, TCP/IP consists of five protocol layers. These protocol layers are related to the seven layers comprising the Open System Interconnection (OSI) network architecture.

Reference Models in Communication Networks

The most important reference models are :

OSI reference model.

TCP/IP reference model.

OSI reference Model

There are many users who use computer network and are located all over the world. To ensure national and worldwide data communication ISO (ISO stands for International Organization of Standardization.) developed this model. This is called a model for open system interconnection (OSI) and is normally called as OSI model.OSI model architecture consists of seven layers. It defines seven layers or levels in a complete communication system.

 

 

TCP/IP reference model

TCP/IP is transmission control protocol and internet protocol. Protocols are set of rules which govern every possible communication over the internet. These protocols describe the movement of data between the host computers or internet and offers simple naming and addressing schemes.

·        NETWORK SECURITY MECHANISM

The process to implement the security properties is known as security mechanism. The various type of mechanism on the basis of properties is as follows:

Attack Prevention

Attack Avoidance

Attack Detection

Attack Prevention: can be defined as a series of security mechanism implemented to prevent or defend against various types of attack before they can actually reach and affect the target systems. An important mechanism is access control which is defined as the process of limiting the access to the resources of the Information System. Access can be implemented at different levels such as the operating system the network and the application layer.

A firewall is also an important access control system that is implemented at the network layer the concept behind firewall is to separate the trusted network from the entrusted network known as internet. The firewall prevents the attack from the outside world against the machines inside the internal network by preventing connections attempts from the unauthorized entities located outside.

Attack Avoidance: The expansion of connectivity of computers makes the need of protecting the message and message from tampering reading important. This is the technique in which the information is modified in a way that makes is unusable for the attacker. This is performed under the assumption that the attacker may have access to the subject system/information. The sender preprocess the information before it is send through the unsecured system and the same is again post processed on the receiver end systems. This encryption and decryption is perfumed by cryptography mechanism, they are further divided in the following forms:

Secret Key Cryptography

Public Key Cryptography

Hash Functions

Attack Detection: In this mechanism it is assumed that the attacker is able to bypass the installed security measures to access the desired target/information. When such incidents happens attack detection takes the responsibility to report someone that something went wrong somewhere in the system.

Attack detection is not an applicable mechanism instead of that it’s a check/measure which will make sure that if anything happened badly in the system then someone should be notified.

 

Software and application of PC software packages: Software definition, Type of software and its Knowledge of Word processing, Spreadsheets and Power point presentation software packages

Software is a set of programs, which is designed to perform a well-defined function. A program is a sequence of instructions written to solve a particular problem.

There are two types of software −

System Software

Application Software

System Software

The system software is a collection of programs designed to operate, control, and extend the processing capabilities of the computer itself. System software is generally prepared by the computer manufacturers. These software products comprise of programs written in low-level languages, which interact with the hardware at a very basic level. System software serves as the interface between the hardware and the end users.

Some examples of system software are Operating System, Compilers, Interpreter, Assemblers, etc.

Application Software

Application software products are designed to satisfy a particular need of a particular environment. All software applications prepared in the computer lab can come under the category of Application software.

Application software may consist of a single program, such as Microsoft’s notepad for writing and editing a simple text. It may also consist of a collection of programs, often called a software package, which work together to accomplish a task, such as a spreadsheet package.

Examples of Application software are the following −

Payroll Software

Student Record Software

Inventory Management Software

Income Tax Software

Railways Reservation Software

Microsoft Office Suite Software

Microsoft Word

Microsoft Excel

Microsoft PowerPoint

 

Word Processing, Spread sheet and Power presentation

  • WORD PROCESSING

A word processor is a software program that is used to create a document, store it electronically, display it on a screen, modify it using commands and characters, and print it on a printer. It also processes paragraph indentation, margin size, font type, font size, font color, and spacing within the document being created. Word processors have replaced typewriters since they allow the user to make a change anywhere in the document without having to retype the entire page. Word processors also come equipped with “spell-check” functions eliminating the need for multiple editors and provide an immediate tool for grammatical correction. Some common word processors include Microsoft Word, AbiWord, Word Perfect, and Open Office.

Three basic functions lay the foundation for most of the customization that is needed to create many word documents.

Character Formatting

Character formatting changes the appearance of individual characters and relates to the size, font, color, and overall style of the letters or numbers being used. Character formatting also involves underlining, italicizing, and making bold those characters being used. This is great for making a word stand out or for underlining book titles.

Paragraph Formatting

Paragraph formatting adjusts the spacing, alignment, and indentation of the paragraphs being formed. Spacing refers to the amount of lines left blank in between the lines being processed. A good example of this is double-spacing which is commonly used in an educational setting where a student has to write a paper for a specific instructor. Commonly double-spacing is used so that the instructor can make corrections to the document without having to mark over the actual words on the paper. Alignment refers to the way the paragraph is positioned in regards to the left and right margins. A left alignment is most commonly used when creating a word document and this setting aligns the words being formed to be flush with the left margin. A center alignment is usually used for titling a paper.

Page Formatting

Page formatting refers to the width of the margins, the size of the paper being used, and the orientation of the page. The standard margin is 1.25 inches on both the left and right but these can be customized to suit need and preference. The paper size options reflect what can be used in the printer, and the orientation indicates whether the document will use the traditional or landscape positioning on that paper. Traditional orientation is 8.5 inches wide by 11 inches tall whereas landscape is the exact opposite at 11 inches wide by 8.5 inches tall.

 

 

Word processing tools

 

Some of the basic tools that are employed in word processing programs that help to make the application more user friendly are tables, graphics, and templates. These tools allow for minimal effort and excellent results when adding features like these to a word document.

Tables

Tables are used for organizing information and are composed of rows and columns in which data is placed. This is great for comparing and contrasting information as it’s condensed and presented in a straight forward fashion. Tables can also be used for laying out entire documents, such as a resume, where information is sectioned off from one another. In this example, the entire report is formulated to a table instead of a small section as mentioned earlier.

Graphics

Graphics are pictures, drawings, clip art, or other images that can be inserted into a document from other programs or from stored data on a computer. This makes for easy illustrations where a picture, or pictures, would suffice better than words or tables to highlight a point. Graphics tools also allow the user to manipulate the images that have been imported by changing the color, contrast, brightness, and size of the image, among other things. The customization process of these images in a word processor provide for an easy and quick avenue of explanation concerning the topics at hand.

Templates

Another useful tool are Templates. These are preprogrammed arrangements of ideas and/or illustrations that are known to serve a purpose and are already organized for the user to interact with. Most often this means “filling in the blanks” and some common templates that should be recognized are resumes, business cards, identification cards, fax cover sheets, memos, invoices, and newsletters

 

  • SPREADSHEETS

 

A spreadsheet is a group of values and other data organized into rows and columns similar to the ruled paper worksheets traditionally used by bookkeepers and accountants.” The spreadsheet software is mandatory to create computerized spreadsheets. Microsoft Excel is a form of a spreadsheet. There are many terms one must have to know to create a spreadsheet. A worksheet is the single spreadsheet document. A workbook allows multiple worksheets to be saved together in a single spreadsheet file. Worksheets are divided into rows and columns. The intersection of a row is called a cell. One must enter content into the active cell, or current cell; it has a border around it to make it be easily identified. Data is entered directly into worksheet cells by clicking a cell to make it the active cell. Labels, constant values, formulas, and functions are the data that is entered into a cell. Before one enters a formula or function into a cell, one must begin with some type of mathematical symbol, usually the equal sign = Spreadsheets are used to organize and calculate data. There is a maximum number of rows and columns in a spreadsheet which varies depending on the version of software you have. It is essential to know how to use spreadsheets for school, work, sports, or anything that requires data!

Tables, graphics, and templates are all available to a user with application software, such as Microsoft Word, Microsoft Excel, and PowerPoint. Tables are ways a user can organize data and information at their convenience. According to Microsoft Word, there are now many different available options for users who are looking for various kinds of tables. These different options include the following: the Graphic Grid, Insert Table, Draw Table, insert a new or existing Excel Spreadsheet table, and Quick Tables. The concept of using tables for data input is relatively simple. In order for a user to insert a table, the user must first open Microsoft Word. Once they have done this, they must click the “table” button to customize the table to achieve their needs. The overall format for a table consists of a large (or small) grid that can be altered by the amount of information the user has, ex. four columns five rows. Next, the user must insert the table into the word document by selecting “insert table” from the dropdown menu. Microsoft Excel contains pivot tables that are tables that include data from a spreadsheet with columns and rows that can be specifically selected.  Graphics in Microsoft Word are pictures, or clip art that are able to be inserted into a Microsoft Word document, Excel Spreadsheet, PowerPoint slide, or any other Office application. the most common graphic used in Excel is graphs. You can create graphs based on data taken from your spreadsheet. Graphics are inserted into these Office Applications to enhance the information presented in a Word Document, Excel worksheet, or PowerPoint slide. A user can insert their own picture through their office documents; add clip art, shapes, SmartArt, screenshot, or Word Art. Templates are pre-constructed document layouts whose primary use is to assist a user in creating a specific type of document in a convenient amount of time. The different options of templates vary, but a few of the following are common ones used every day: agendas, brochures, calendars, flyers, fax covers, and many more. Templates are used to save a user time, and confusion in creating their document.

Using of Spreadsheet

Chart

A chart can be created as its own object or embedded within the sheet itself. This is helpful when a user needs to analyze data or represent changing data. Some form of charts are: lines graphs, scatter plot charts, bar charts, Venn diagram charts, and the list goes on.

Function

A function is a pre-programmed mathematical formula to allow the user to make calculations based on the data input. The functions under spreadsheets are there to perform a simple calculation by using a certain value, called arguments.

There are many different reasons to have functions on spreadsheets. One would be for arithmetic functions to process numerical data. The next would be statistical functions that use analysis tools and averaging tools. This would be useful for finding the average of the numbers in a certain row/column on a spreadsheet. The next function is date that processes and converts dates. This function could be used to put the sequential dates in order on the spreadsheet.

Formulas

A formula identifies the calculation needed to place the result in the cell it is contained within. This means a cell has two display components; the formula itself and the resulting value. Typically, a formula consists of five expressions: value, references, arithmetic operations, relation operations, and functions. By using these expressions, formulas can help to make tables, solve math problems, calculate a mortgage, figure out accounting tasks, and many other business-related tasks that use to be done tediously on paper

Cell Referencing

Cell referencing refers to the ability to utilize a cell or range of cells in a spreadsheet and is commonly used to create formulas to calculate data. Formulas can retrieve data from one cell in the worksheet, different areas of the worksheet, or different cells throughout an entire workbook.

 

Pivot Tables

One the most powerful features available in the Microsoft Office spreadsheet program Excel, is pivot tables. Pivot tables allow you to manipulate large amounts of raw data. It makes it easy to analyze the data in different ways, with a simple click and drag. Vast quantities of data can be summarized in a variety of ways. Calculations can be performed by row or column. Data can be filtered or sorted automatically by any or all of the fields. Excel can even recommend a basic layout of a pivot table based on the type of data selected.

 

POWERPOINT

Powerpoint is a Microsoft Office software used to present information and work as a visual aide. Powerpoint make it easy to organize and present information in a visually appealing way such as charts, pictures, tables, video clips, and sounds. Various Designs and color themes come are built in the software and ready to use. The slides themselves come with several options of pre-loaded layouts, using features such as bullet points, pictures, captions, and titles – These are easy to drag and drop to make rearranging very easy. The idea of a digital visual is to help a presenter engage their audience and display their ideas in a more simple form. One feature that comes in handy is the ability to print the slides so either the presenter or audience can be informed ahead of time of what to expect. Powerpoint also has a notes feature in which you can input notes you may need for your presentation. The notes feature also allows you to print out the notes page with the slide show on it which is known as notes view. You can also adjust the size of the slide on the notes view so that all of your notes fit on the page and looks presentable. If all of your notes do not fit on the notes page provided, it will spill over to the next page. If you know their is a lot of wording, you can make a duplicate slide and hide it in the presentation, so you will have more room for your notes! Teachers, employers, and computer users all over the world have now become accustomed to using PowerPoint as their “go-to” visual aide. The image on the right shows a presenter using a powerpoint as a visual aide.

The PowerPoint presentation graphics program provides the user with several assortment tools and operations for creating and editing slides. With those tools, one is able to add new or delete old slides that are previewed in the slide thumbnail tab area, usually found on the left side of the screen. One is also able to switch to the slide outline tab, which contains only the title and the main text included in the slide. If desired, using the Insert tab, the user can perform additional operations like exporting images, along with adding formatted tables, shapes, symbols, charts, and much more to better express their message. Additionally, to customize the PowerPoint to make it even more dynamic and presentable, text can be animated, and a unique transition can be added to the slides. With animation, text can be set to appear in a specific way in the slide during a slide show. Tons of special effects are provided for the user, including animations to make the text to fly, dissolve, fly, float, or bounce in. Similarly, one is also able to apply special effects to specific slides to transition from one slide to another in a specific manner. Additionally, Microsoft PowerPoint allows recorded narration to be played back as the slideshow is being presented, along with speaker notes. Furthermore, most presentation graphics programs also allow the user to print those speaker notes for the targeted audience’s convenience.

 

 

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