76ibps So-it Officer-computer Cracker

7/24/2019 76ibps So-it Officer-computer Cracker

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IBPS SO:IT OFFICER COMPUTER CRACKER

IT OFFICER COMPUTER AWARENESS

1. Basic Computer 2. Computer Network

3. Database Management System 4. Data structure

5. Operating System

System of interconnected computers and computerized peripherals such as

printers is called computer network .This interconnection among computers

facilitates information sharing among them. Computers may connect to eachother by either wired or wireless media.

Characteristics of a Network-A network is a group of systems that are

connected to allow sharing of resourcessuch as files or printersor sharing

of services-such as an Internet connection .There are two aspects of setting up anetwork: the hardware used to connect the systems together and the software installed on the computers to

allow them to communicate.

Servers-The server is a special computer that contains more disk space and memory than are found on client

workstations. The server has special software installed that allows it to function as a server. This specialsoftware can provide file and print services (to allow sharing of files and printers), provide web pages toclients, or provide e-mail functionality to the company.

Workstations -The workstation also is known as a client, which is just a basic computer running a client

operating system such as Windows XP or Linux. These users typically store their files on a central server so

that they can share the files with other users on the network.

Hosts-The term hostrefers to any computer or device that is connected to a network and sends or receives

information on that network. A host can be a server, a workstation, a printer with its own network card, or adevice such as a router. We can summarize by saying that any system ordevice that is connected to the network is known as a host.

Types of Networks-

Organizations of different sizes, structures, and budgets need differenttypes of networks. Networks can be divided into one of two categories:

peer-to-peer or server-based networks.

1. Peer-to-Peer Network

2. Server-Based Networks

Computer Network

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Peer-to-Peer Network-A peer-to-peer network has no dedicated servers instead; a number of workstations

are connected together for the purpose of sharing information or devices. When there is no dedicated server, all

workstations are considered equal; any one of them can participate as the client or the server. Peer-to-peernetworks are designed to satisfy the networking needs of home networks or of small companies that do not

want to spend a lot of money on a dedicated server but still want to have the Capability to share information or

devices. For example, A small peer-to-peer network will allow these three computers to share the printer andthe customer information with one another .The extra cost of a server was not incurred because the existing

client systems were networked together to create the peer-to-peer network.A big disadvantage of peer-to-peernetworking is that you cant do your day-today administration in a single place.

Server-Based Networks-Usually after four or five systems

have been networked, the need for a dedicated server to store all

of the user accounts and data files becomes apparentthis is a

server-based network. The advantage of a server-based networkis that the data files that will be used by all of the users are

stored on the one server. This will help you by giving you a

central point to set up permissions on the data files, and it will

give you a central point from which to back up all of the data incase data loss should occur. With a server-based network, the

network server stores a list of users who may use networkresources and usually holds the resources as well. The server in

a server-based network may provide a number of different

services. The services it will offer to the network usually are decided by the servers role. There are a numberof different roles that a server could play on a network:

1. File and print servers 2. Application servers 3. Web servers 4. Directory servers

1. File and print servers-:File and print servers control, share printers

and files among clients on the network. File and print servers were the

original reason to have a network; a large number of users neededaccess to the same files, so the files were placed on a server, and all

clients were connected to the server when they needed to work with thefiles.

2. Application servers-:Application serversare servers that run some form of special program on the server. A

good example of an application server is a server that runs the companys e-mail server. The e-mail server

software is special software that can be run on a server operating system. Another example of software thatwould run on an application server is a database server product such as Microsoft SQL Server. A databaseserver is a server that holds the companys core business data and typically gives this data to custom

applications that run on the workstations. These are some applications that you might find on an applicationserver:

1. Microsoft SQL Server 2.Oracle 3.Microsoft Exchange Server

4. IBM Lotus Domino

3. Web servers-:

Web servers are servers that run the Hypertext Transfer Protocol (HTTP) and are designed topublish information on the Internet or the corporate intranet. Web servers are popular in todays businessesbecause they host web applications (web sites) for the organization. These web applications could be designedfor internal use, or they could be used to publish information to the rest of the world on the Internet. Examples

of web server software are Microsofts Internet Information Services that runs on Windows or Apache webserver software that runs on UNIX/Linux, Novell NetWare, and Windows.

4. Directory servers-Directory servers hold a list of the user accounts that are allowed to log on to the

network. This list of user accounts is stored in a database (known as the directory database) and can store



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information about these user accounts such as address, city, phone number, and fax number. A directoryservice is designed to be a central database that can be used to store everything about such objects as users andprinters.

Ethernet-:Ethernet is a widely deployed LAN technology. This technology was invented by Bob Metcalfe and

D.R. Boggs in the year 1970. It was standardized in IEEE 802.3 in 1980. Ethernet shares media. Network

which uses shared media has high probability of data collision. Ethernet uses Carrier Sense MultiAccess/Collision Detection (CSMA/CD) technology to detect collisions. On the occurrence of collision in

Ethernet, all its hosts roll back, wait for some random amount of time, and then re-transmit the data. Ethernet

connector is network interface card equipped with 48-bits MAC address. This helps other Ethernet devices toidentify and communicate with remote devices in Ethernet. Traditional Ethernet uses 10BASE-T

specifications. The number 10 depicts 10MBPS speed, BASE stands for baseband, and T stands for ThickEthernet. 10BASE-T Ethernet provides transmission speed up to 10MBPS and uses coaxial cable or Cat-5

twisted pair cable with RJ-5 connector. Ethernet follows Star topology with segment length up to 100 meters.

All devices are connected to a hub/switch in a star fashion.

Fast-Ethernet-:

To encompass need of fast emerging software and hardware technologies, Ethernet extends

itself as Fast-Ethernet. It can run on UTP, Optical Fiber, and wirelessly too. It can provide speed up to

100MBPS. This standard is named as 100BASE-T in IEEE 803.2 using Cat-5 twisted pair cable. It usesCSMA/CD technique for wired media sharing among the Ethernet hosts and CSMA/CA (CA stands for

Collision Avoidance) technique for wireless Ethernet LAN. Fast Ethernet on fiber is defined under 100BASE-FX standard which provides speed up to 100MBPS on fiber. Ethernet over fiber can be extended up to 100

meters in half-duplex mode and can reach maximum of 2000 meters in full-duplex over multimode fibers.

Giga-Ethernet-:After being introduced in 1995, Fast-Ethernet retained its high speed status only for three

years till Giga-Ethernet introduced. Giga-Ethernet provides speed up to 1000 mbits/seconds. IEEE802.3ab

standardizes Giga-Ethernet over UTP using Cat-5, Cat-5e and Cat-6 cables. IEEE802.3ah defines Giga-Ethernet over Fiber.

Internet, Intranet and Extranet-:

Internet Intranet Extranet

Internet If you wish to expose

information to everyone in theworld, then you would build an

Internet-type application. AnInternet-type applicationUses Internet protocols such as

HTTP, FTP, or SMTP and isavailable to persons anywhereon the Internet. We use the

Internet and web applications

as ways to extend who the

application can reach. Forexample, I no longer need to go

to the bank to transfer funds.

Because the bank has built aweb site on the Internet, I can

do that from the comfort of my

own home.

Intranet An application is considered to

be on the companys intranet if it is usingInternet-type protocols such as HTTP or

FTP but the application is available only

within the company. The information on acompanys intranet would not be

accessible to persons on the Internetbecause it is not for public use. Forexample, a few years ago I was sitting

with my banking officer going over my

account and noticed that the bank hadmoved all of its customer account

information to a web site and that the

banking officer was using a Web browserto retrieve my account details. Although

the application was being used by a web

browser, it was still an internal

application meant only for bankingofficers.

Extranet From time to time, an

application that has been builtfor the Companys intranet and

used by internal employees will

need to be extended to selectbusiness partners or customers.

If you extend your intranet out

to select business partners orcustomers, you have created an

extranet. An extranet cannot be

used by anyone else external tothe company except for those

selected individuals.



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Network Topologies-:A network topology is the physical layout of computers, cables, and other components

on a network. There are a number of different network topologies, and a network may be built using multiple

topologies. The different types of network layouts are1. Bus topology 2.Star topology 3.Mesh topology 4. Ring topology 5. Hybrid topology6. Wireless topology

Network Media and Connectors-:Cabling is the medium for the transmission of data between hosts on the

LANs. LANs can be connected together using a variety of cable types, such as unshielded twisted-pair, coax,or fiber. Each cable type has its own advantages and disadvantages, which you will examine in this section.

There are three primary types of cable media that can be used to connect systems to a networkcoaxial cable,twisted-pair cable, and fiber-optic cable. Transmission rates that can be

supported on each of these physical media are measured in millions of bits

per second, or megabits per second (Mbps).

Coaxial Cable-:Coaxial, or coax, cable looks like the cable used to bring

the cable TV signal to your television. One strand (a solid-core copper

wire) runs down the middle of the cable. There are two types of coaxcabling: thinnet and thicknet. The two differ in thickness and maximum

cable distance that the signal can travel.

Twisted-Pair Cable-:

Coaxial cable is not as popular today as it was a few years ago; today the popularity

contest has been dominated by twisted-pair cabling. Twisted-pair cabling gets its name by having four pairs ofwires that are twisted to help reduce crosstalk or interference from outside electrical devices. (Crosstalk isinterference from adjacent wires.) there are two forms of twisted-pair cablingunshielded twisted-pair (UTP)

and shielded twisted-pair (STP).

Fiber-Optic Cable-:The third type of cabling that we want to discuss is

fiber-optic cabling. Fiber-optic cabling is unlike coax and twisted-pair,because both of those types have a copper wire that carries the electrical

signal. Fiber-optic cables use optical fibers that carry digital data signalsin the form of modulated pulses of light. An optical fiber consists of anextremely thin cylinder of glass, called the core, surrounded by aconcentric layer of glass, known as the cladding. There are two fibers per

cable-one to transmit and one to receive. The core also can be an optical-quality clear plastic, and the cladding can be made up of gel that reflectssignals back into the fiber to reduce signal loss. There are two types of

fiber-optic cables: single-mode fiber (SMF) and multimode fiber (MMF).

1. Single-mode fiber Uses a single ray of light, known as a mode, tocarry the transmission over long distances.

2. Multimode fiber Uses multiple rays of light (modes) simultaneously, with each ray of light running at a

different reflection angle to carry the transmission over short distances

Cable Max Distance Tr ansfer Rate Connector Used

Thinnet 185 m 10 Mbps BNC

Thicknet 500 m 10 Mbps AUI

CAT 3 (UTP) 100 m 10 Mbps RJ-45

CAT 5 (UTP) 100 m 100 Mbps RJ-45

CAT 5e 100 m 1 Gbps RJ-45

CAT 6 100 m 10 Gbps RJ-45

Fiber 2 km 1+ Gbps SC, ST



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Network devices-:Network devices are components used to connect computers or other electronic devices

together so that they can share files or resources like printers or fax machines. Devices used to setup a Local

Area Network (LAN) are the most common types of network devices used by the public. A LAN requires ahub, router, cabling or radio technology, network cards, and if online access is desired, a high-speed

modem. This is much less complicated than it might sound to someone new to networking.

HUB-:A hub is used in a wired networkto connect Ethernet cables from

a number of devices together. The hub allows each device to talk to theothers. Hubs arent used in networks with only wireless connections, since

network devices such as routers and adapters communicate directly withone another. Hubs are such simple devices they require no

configuration, and have no manuals that their function is now included

in other devices such as routers and modems.

Router-:A routeris a communications device that connects multiple

computers or other routers together and transmits data to its correctdestination on the network. A router can be used on any size of network.

On the largest scale, routers along the Internet backbone forward datapackets to their destination using the fastest available path. For smaller

business and home networks, a router allows multiple computers to sharea single high-speed Internet connection such as through a cable modemor DSL modem. These routers connect from 2 to 250 computers. To

prevent unauthorized users from accessing files and computers, many

routers are protected by a built-in antivirus protection. Routers alsosupport wireless communications, eliminating the need for a separate

wireless access point in a wireless network. If network has a separate

wireless access point, it connects to the router via a cable. Some routers

also include additional functionality such as including a built-in print server.

Modem-:A computers digital signals must be converted to analog signals

before they are transmitted over standard telephone lines. The

communications devices that perform this conversion in a modem,

sometimes called a dial-up modem. The word, modem, is derived from thecombination of the words, modulation, to change into an analog signal,

and demodulation,to convert an analog signal into a digital signal. Both the

sending and receiving ends o a standard telephone line (communicationschannel) must have a dial-up modem or data transmission to occur. For

example, a dial-up modem connected to a sending computer converts the

computers digital signals into analog signals. The analog signals then can travel over a standard telephoneline. At the receiving end, another dial-up modem converts the analog signals

back into digital signals that a receiving computer can process.

Bridge-:A bridge reads the outermost section of data on the data packet, to

tell where the message is going. It reduces the traffic on other networksegments, since it does not send all packets. Bridges can be programmed to

reject packets from particular networks. Bridging occurs at the data link layerof the OSI model, which means the bridge cannot read IP address, but only

the outermost hardware address of the packet. In our case the bridge can read



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the Ethernet data which gives the hardware address of the destination address, not the IP address. Bridgesforward all broadcast messages. Only a special bridge called a translation bridge will allow two networks of

different architectures to be connected. Bridges do not normally allow connection of networks with different

architectures. The hardware address is also called the MAC (media access control) address. To determine thenetwork segment a MAC address belongs to, bridges use one of the following

Transparent Bridging:They build a table of addresses (bridging table) as they receive packets. If the

address is not in the bridging table, the packet is forwarded to all segments other than the one it came from.This type of bridge is used on Ethernet networks.

Source Route Bridging:

The source computer provides path information inside the packet. This is used onToken Ring networks. A gateway can translate information between different network data formats or networkarchitectures. It can translate TCP/IP to AppleTalk so computers supporting TCP/IP can communicate with

Apple brand computers. Most gateways operate at the application layer, but can operate at the network or

session layer o the OSI model. Gateways will start at the lower level and strip information until it gets to therequired level and repackage the information and work its way back toward the hardware layer of the OSI

model. To confuse issues, when talking about a router that is used to interface to another network, the word

gateway is often used. This does not mean the routing machine is a gateway as defined here, although it could

be.

OSI Reference Model:

OSI (Open Systems Interconnection) is reference model for how messages shouldbe transmitted between any two points in a telecommunication network. A reference model is a framework for

understanding relationships. The purpose of the OSI reference model is to guide vendors and developers so

that the digital communication products and software programs they create will interoperate. The OSIreference model defines seven layers of functions that take place at each end of a communication.

Layers of OSI -:

Layer 7-:The application layer - This is the layer at

which communication partners are identified,quality of service (QoS) is identified, user

authentication and privacy are considered, and any

constraints on data syntax are identified. (This layeris not the application itself, although some

applications may perform application layer

functions.)

Layer 6-:The presentation layer - This is a layer, usually part of an operating system (OS), that converts

incoming and outgoing data from one presentation format to another (for example, from a text stream into a

popup window with the newly-arrived text).

Layer 5-:The session layer - This layer sets up, coordinates, and terminates conversations, exchanges, and

dialogs between the applications at each end. It deals with session and connection coordination.

Layer 4-:The transport layer - This layer manages the end-to-end control (for example, determining whether all

packets have arrived) and error-checking. It ensures complete data transfer.

Layer 3-:



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The network layer - This layer handles the routing of the data (sending it in the right direction to theright destination on outgoing transmissions and receiving incoming transmissions at the packet level). Thenetwork layer does routing and forwarding.

Layer 2-:The data-link layer - This layer provides synchronization for the physical level and does bit-stuffing

for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management. This layer hastwo sub layers, the Logical Link Control Layer and the Media Access Control Layer.

Layer 1-:The physical layer - This layer conveys the

bit stream through the network at the electrical andmechanical level. It provides the hardware means of

sending and receiving data on a carrier network.

TCP/IP Model -:The Transmission Control Protocol

/ Internet Protocol (TCP/IP) was created by the

Department of Defense (DoD) to make sure andprotect data integrity, and also maintained

communications in the time of disastrous war.However, if designed and deployed properly

according to standard, a TCP/IP network can be a

truly reliable and flexible one. Essentially, theDepartment of Defense (DoD) Model is a reduced version of the OSI Reference Model. The DoD model basedon four layers:

Layer Description Protocols

4.

Application

Defines TCP/IP application protocols and how host

programs interface with transport layer services touse the network.

HTTP, Telnet, FTP, TFTP,

SNMP, DNS, SMTP,X Windows, other

application protocols

3. Transport Provides communication session management

between host computers. Defines the level of service

and status of the connection used when transportingdata.

TCP, UDP, RTP

2. Internet Packages data into IP datagram, which contain

source and destination address information that is

used to forward the datagrams between hosts andacross networks. Performs routing of IP datagrams.

IP, ICMP, ARP, RARP

1. Network

interface/

Access

Specifies details of how data is physically sentthrough the network, including how bits are

electrically signaled by hardware devices that

interface directly with a network medium, such ascoaxial cable, optical fiber, or twisted-pair copper

wire.

Ethernet, Token Ring,FDDI, X.25, Frame Relay,

RS-232, v.35

IP Address-:Every machine on a network has a unique identifier. Most networks today, including all

computers on the Internet, use the TCP/IP protocol as the standard for how to communicate on the network. Inthe TCP/IP protocol, the unique identifier for a computer is called its IP address.



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There are two standards for IP addresses:-1) IP Version 4 (IPv4) 2) IP Version 6 (IPv6).

All computers with IP addresses have an IPv4 address, and many are starting to use the new IPv6 address

system as well. Here's what these two address types mean:-IPv4 uses 32 binarybits to create a single unique address on thenetwork. An IPv4 address is expressed by four numbers separated

by dots. Each number is the decimal (base-10) representation foran eight-digit binary (base-2) number, also called an octet. Forexample: 216.27.61.137.Class A - 0.0.0.0 - 127.255.255.255

Class B - 128.0.0.0 - 191.255.255.255

Class C - 192.0.0.0 - 223.255.255.255Class D - 224.0.0.0 - 239.255.255.255

Class E - 240.0.0.0 - 247.255.255.255

IPv6 uses 128 binary bits to create a single unique address onthe network. An IPv6 address is expressed by eight groups of

hexadecimal (base-16) numbers separated by colons, as in 2001:cdba: 0000:0000:0000:0000:3257:9652Groups of numbers that

contain all zeros are often omitted to save space, leaving a colonseparator to mark the gap (as in 2001:cdba::3257:9652).

At the dawn of IPv4 addressing, the Internet was not the large commercial sensation it is today, and mostnetworks were private and closed off from other networks around the world. When the Internet exploded,

having only 32 bits to identify a unique Internet address caused people to panic that we'd run out of IP

addresses. Under IPv4, there are 232 possible combinations, which offer just under 4.3 billion uniqueaddresses. IPv6 raised that to a panic-relieving 2128 possible addresses.

Web browser- :

A browser is an application program that provides a way to look at and interact with all theinformation on the World Wide Web. The word "browser" seems to have originated prior to the Web as ageneric term for user interfaces that let you browse text files online. Technically, a Web browser is a client

program that uses HTTP to make requests of Web servers throughout the Internet on behalf of the browseruser. Most browsers support e-mail and the File Transfer Protocol but a Web browser is not required for those

Internet protocols and more specialized client programs are more popular. The first Web browser, called WorldWide Web, was created in 1990. That browser's name was changed to Nexus to



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avoid confusion with the developing information space known as the World Wide Web. The first Webbrowser with a graphical user interface was Mosaic, which appeared in 1993. Many of the user interfacefeatures in Mosaic went into Netscape Navigator. Microsoft followed with its Internet Explorer (IE).

Bandwidth -:Bandwidth describes the rate at which data can be transferred to your computer from a website

or internet service within a specific time. Therefore the amount of bandwidth you have (the bandwidth'strength') determines the efficiency and speed of your internet activity that is, when you open web pages,

download files and so on. A useful analogy is a pipe with water running through it the wider the pipe, the

greater the volume of water that can flow through it. The same applies to bandwidth strength and the flow ofthe volume of data. Bandwidth is generally measured in bits per second' or sometimes bytes per second'.

ARPANET- :

Advanced Research Projects Agency Network, ARPANET or ARPAnet began development

in 1966 by the United States ARPA. ARPANET was a Wide Area Network linking many Universities andresearch centers, was first to use packet switching, and was the beginning of what we consider the Internet

today. Some of the reasons for creating ARPANET include making it easier for people to access computers, to

improve computer equipment, and to have a more effective communication method for the military.

Bookmark - :When referring to the Internet or a browser, a bookmark or electronic bookmark is a method of

saving a web page's address. For example, with most browsers pressing Ctrl + D will bookmark the page you

are viewing.

Bounce - :A description of what occurs when an e-mail message returns back to the sender as undeliverable.

Some e-mail programs also have a bounce or bounce back feature built into them, which allows the user tobounce messages back to the sender causing the e-mail address to appear invalid.

Cyber Law-:Cyber law is the part of the overall legal system that deals with the Internet, cyberspace, and

their respective legal issues. Cyber law covers a fairly broad area, encompassing several subtopics includingfreedom of expression, access to and usage of the Internet, and online privacy. Generically, cyber law has beenreferred to as the Law of the Internet.

DNS-:Domain Name Systemor Domain Name Service, a DNS is an Internet or other network server that

helps to point domain names or the hostname to their associated IP address that was introduced by PaulMockapetris and Jon Postel in1984. If a domain name is not found within the local database, the server may

query other domain servers to obtain the address of a domain name. For example, when a user is accessing the

ibtindia domain a user would enter the easy to remember domain: ibtindia.com. When entered that domainname is looked up on a Domain Name System to translate that name into an IP address that can be better

understood by computer, e.g. 69.72.169.241. Using that IP address the computers can then find the computer

containing the ibtindia web page and forward that information to your computer.

Phishing-:Pronounced like fishing, phishing is a term used to describe a

malicious individual or group of individuals scamming users by sending

e-mails or creating web pages that are designed to collect an individual's

online bank, credit card, or other login information. Because these e-mailsand web pages look like legitimate companies users trust them and enter

their personal information.



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Search engine-:A search engine is a software program or script

available through the Internet that searches documents and files for

keywords and returns the results of any files containing those keywords.Today, there are thousands of different search engines available on the

Internet, each with their own abilities and features. The first search

engine ever developed is considered Archie, which was used to search forFTP files and the first text-based search engine is considered Veronica.

Today, the most popular and well known search engine is Google.

Firewall-:A firewall is a software utility or hardware device that limits outside network access to a computer

or local network by blocking or restricting network ports. Firewalls are a great step for helping prevent un-

authorized access to a company or home network. The picture is an example of a hardware firewall, the

ZyXEL ZyWALL a Unified Security Gateway with a Firewall and other security features. In addition tohardware firewalls like that shown above, basic hardware firewalls are also commonly found in most network

routers and can be configured and setup through the router setup. Software firewalls are designed to protect the

computer they are installed onto by blocking any unrestricted programs from sending and receiving

information from the network or Internet. A good example of a software Firewall is the Windows Firewall thatis included with Microsoft Windows.

Hacking-:

Hacking in simple terms means an illegal intrusion into acomputer system and/or network. There is an equivalent term tohacking i.e. cracking, but from Indian Laws perspective there is no

difference between the term hacking and cracking. Every act

committed towards breaking into a computer and/or network ishacking. Hackers write or use ready-made computer programs to

attack the target computer. They possess the desire to destruct and

they get the kick out of such destruction. Some hackers hack for

personal monetary gains, such as to stealing the credit card

information, transferring money from various bank accounts to theirown account followed by withdrawal of money. They extort money

from some corporate giant threatening him to publish the stoleninformation which is critical in nature.

Message Switching-:In this switching method, a different strategy is used, where instead of

establishing a dedicated physical line between the sender and the

receiver, the message is sent to the nearest directly connected switchingnode. This node stores the message, checks for errors, selects the best

available route and forwards the message to the next intermediate node.

The line becomes free again for other messages, while the process isbeing continued in some other nodes. Due to the mode of action, this

method is also known as store-and-forward technology where themessage hops from node to node to its final destination. Each nodestores the full message, checks for errors and forwards it. In this

switching technique, more devices can share the network bandwidth, as

compared with circuit switching technique. Temporary storage ofmessage reduces traffic congestion to some extent. Higher priority can be given to urgent messages, so that the

low priority messages are delayed while the urgent ones are forwarded faster. Through broadcast addresses onemessage can be sent to several users. Last of all, since the destination host need not be active when the

message is sent, message switching techniques improve global communications.



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Packet Switching -:

The basic approach is not much

different from message switching. It is also based on thesame store-and-forward approach. However, to overcome

the limitations of message switching, messages are divided

into subsets of equal length called packets. This approachwas developed for long-distance data communication(1970) and it has evolved over time. In packet switching

approach, data are transmitted in short packets (fewKbytes). A long message is broken up into a series ofpackets as shown in Fig. Every packet contains some

control information in its header, which is required forrouting and other purposes. Main difference betweenPacket switching and Circuit Switching is that the

communication lines are not dedicated to passing messagesfrom the source to the destination. In Packet Switching,different messages (and even different packets) can pass

through different routes, and when there is a "dead time" in the communication between the source and the

destination, the lines can be used by other sources.

Circuit switching-:

A networking technology that provides a

temporary, but dedicated, connection between two stations nomatter how many switching devices the data are routed

through. Circuit switching was originally developed for the

analog-based telephone system in order to guarantee steady,consistent service for two people engaged in a phone

conversation. Analog circuit switching Frequency DivisionMultiplexing(FDM)has given way to digital circuit switchingTime Division Multiplexing (TDM), and the digital

counterpart still maintains the connection until broken.

Encryption and Decryption-:Encryption is the process of translating plain text data (plaintext) into

something that appears to be random and meaningless (ciphertext). Decryption is the process of converting

ciphertext back to plaintext. To encrypt more than a small amount of data, symmetric encryption is used. Asymmetric key is used during both the

encryption and decryption processes. To decrypt

a particular piece of ciphertext, the key that wasused to encrypt the data must be used. The goal

of every encryption algorithm is to make it as

difficult as possible to decrypt the generatedciphertext without using the key. If a really good

encryption algorithm is used, there is no

technique significantly better than methodically trying every possible key. For such an algorithm, the longerthe key, the more difficult it is to decrypt a piece of ciphertext without possessing the key. It is difficult todetermine the quality of an encryption algorithm. Algorithms that look promising sometimes turn out to be

very easy to break, given the proper attack. When selecting an encryption algorithm, it is a good idea to chooseone that has been in use for several years and has successfully resisted all attacks.

Private Key encryption -:

Private Key encryption -Private Key means that each computer has a secret key(code) that it can use to encrypt a packet of information before it is sent over the network to the othercomputer. Private key requires that you know which computers will talk to each other and install the key on



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each one. Private key encryption is essentially the same as a secret code that the two computers must eachknow in order to decode the information. The code would provide the key to decoding the message. Think of itlike this. You create a coded message to send to a friend where each letter is substituted by the letter that is

second from it. So "A" becomes "C" and "B" becomes "D". You have already told a trusted friend that thecode is "Shift by 2". Your friend gets the message and decodes it. Anyone else who sees the message will onlysee nonsense.

Public key encryption -:Public key encryption uses a combination of a private key and a public key. The

private key is known only to your computer while the public key is given by your computer to any computerthat wants to communicate securely with it. To decode an encrypted message, a computer must use the public

key provided by the originating computer and it's own private key.

Digital signature-:A digital signature is basically a way to ensure that an electronic document (e-mail,

spreadsheet, text file, etc.) is authentic. Authentic means that you know who created the document and you

know that it has not been altered in any way since that person created it. Digital signatures rely on certain types

of encryption to ensure authentication. Encryption is the process of taking all the data that one computer is

sending to another and encoding it into a form that only the other computer will be able to decode.Authentication is the process of verifying that information is coming from a trusted source. These two

processes work hand in hand for digital signatures.

Unicasting, Multicasting and Broadcasting? If the message is sent from a source to a single destination node, it is called Unicasting. If the message is sent to some subset of other nodes, it is called Multicasting. If the message is sent to all the m nodes in the network it is called Broadcasting.

What is Project 802?It is a project started by IEEE to set standards to enable

intercommunication between equipment from a variety ofmanufacturers. It is a way for specifying functions of the

physical layer, the data link layer and to some extent thenetworklayer to allow for interconnectivity of major LAN protocols.

It consists of the following:

802.1 is an internetworking standard for compatibility ofdifferent LANs and MANs across protocols.

802.2 Logical link control (LLC) is the upper sublayer of thedata link layer which is non-architecture-specific, that is

remains the same for all IEEE-defined LANs. Media access

control (MAC) is the lower sublayer of the data link layerthat contains some distinct modules each carrying

proprietary information specific to the LAN product being

used. The modules are Ethernet LAN (802.3), Token ring

LAN (802.4), Token bus LAN (802.5). 802.6 is distributedqueue dual bus (DQDB) designed to be used in MANs.



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Database-:A database is a logically coherent collection of data with some inherent meaning, representing

some aspect of real world and which is designed, built and populated with data for a specific purpose.

DBMS-:It is a collection of programs that enables user to create and maintain a database. In other words it is

general-purpose software that provides the users with the processes of defining, constructing and manipulating

the database for various Applications.

Advantages of DBMS-:1. Redundancy is controlled. 2. Unauthorized access is restricted.3. Providing multiple user interfaces. 4. Enforcing integrity constraints.

5. Providing backup and recovery.

III-tier Architecture -:

Three levels of data abstraction (III-tier Architecture)-:They are three levels of abstraction are given below,

1.

Physical level: The lowest level of abstractiondescribes how data are stored. (How to store the

data?)2. Logical level: The next higher level of abstraction,

describes what data are stored in database and what

relationship among those data. (What type of data to

be stored?)3. View level: The highest level of abstraction describes

only part of entire database. (How to show the data?)

Integrity rules-:There are two types of Integrity rules

1. Entity Integrity:States that "Primary key cannot have NULL value"

2. Referential Integrity:States that "Foreign Key can be either a NULL value or should be PrimaryKey value of other relation.

Data Independence-:Data independence means that "the application is independent of the storage structure

and access strategy of data". In other words, the ability to modify the schema definition in one level should notaffect the schema definition in the next higher level.

Two types of Data Independence:1. Physical Data Independence: Modification in physical level should not affect the logical level.

2. Logical Data Independence: Modification in logical level should affect the view level.

The people who use the database can be categorized -

a) Database users b) Database administrator (DBA)

Database users are of 4 different types that are given below:

1) Naive users:These are the unsophisticated users who interact with the system by invoking one of the

application programs that have been written previously. E.g. consider a user who checks for account balance

information over the World Wide Web. Such a user access a form, enters the account number and passwordetc. And the application program on the internet then retrieves the account balance using given accountinformation which is passed to the user.

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2) Application programmers-:These are computer professionals who write application programs, used to

develop user interfaces. The application programmer uses Rapid Application Development (RAD) toolkit or

special type of programming languages which include special features to facilitate generation of forms anddisplay of date on screen.

3) Sophisticated users-:

These users interact with the database using database query language. They submittheir query to the query processor. Then Data Manipulation Language (DML) functions are performed on the

database to retrieve the data. Tools used by these users are OLAP (Online Analytical Processing) and data

mining tools.

4) Specialized users-:These users write specialized database applications to retrieve data. These applications

can be used to retrieve data with complex data types e.g. graphics data and audio data.

b) Database Administrator (DBA):

A person having who has central control over data and programs that

access the data is called DBA. DBA functions are given below:

1) Schema definition: DBA creates database schema by executing Data Definition Language (DDL)statements.

2) Storage structure and access method definition3) Schema and physical organization modification: If any changes are to be made in the original

schema, to fit the need of your organization, then these changes are carried out by the DBA.

4) Granting of authorization for data access: DBA can decide which parts of data can be accessed bywhich users. Before any user access the data, dbms checks which rights are granted to the user bythe DBA.

5) Routine maintenance: DBA has to take periodic backups of the database, ensure that enough diskspace is available to store new data, ensure that performance of dbms ix not degraded by anyoperation carried out by the users.

SQL-:SQL stands for Structured Query Language. SQL is used to communicate with a database.

According to ANSI (American National Standards Institute), it is the standard language for relational databasemanagement systems. SQL statements are used to perform tasks such as update data on a database, or retrievedata from a database. Some common relational database management systems that use SQL are: Oracle,Sybase, Microsoft SQL Server, Access, Ingres, etc. Although most database systems use SQL, most of them

also have their own additional proprietary extensions that are usually only used on their system. However, thestandard SQL commands such as "Select", "Insert", "Update", "Delete", "Create", and "Drop" can be used toaccomplish almost everything that one needs to do with

a database. This tutorial will provide you with the

instruction on the basics of each of these commands aswell as allow you to put them to practice using the SQL

Interpreter.

Relational Model-:

The most popular data model inDBMS is the Relational Model. It is more scientific a

model than others. This model is based on first-orderpredicate logic and defines a table as an n-array relation.

The main highlights of this model are

1. Data is stored in tables called relations.2. Relations can be normalized.3. In normalized relations, values saved are

atomic values.



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4. Each row in a relation contains a unique value.5. Each column in a relation contains values from a same domain.

Key-:

A key is an attribute (also known as column or field) or a combination of attribute that is used to identifyrecords. Sometimes we might have to retrieve data from more than one table, in those cases we require to jointables with the help of keys. The purpose of the key is to bind data together across tables without repeating all

of the data in every table. Such an attribute is called a key attribute, and its values can be used to identify eachentity uniquely. For example, the Name attribute is a key of the COMPANY entity type because no twocompanies are allowed to have the same name. For the PERSON entity type, a typical key attribute is

SocialSecurityNumber. Sometimes, several attributes together form a key, meaning that the combination of theattribute values must be distinct for each entity. If a set of attributes possesses this property, we can define acomposite attribute that becomes a key attribute of the entity type. The various types of key with e.g. in SQL

are mentioned below, (For examples let suppose we have an Employee Table with attributes ID , Name

,Address , Department_ID ,Salary)

(I) Super Key :An attribute or a combination of attribute that is used to identify the records uniquely is

known as Super Key. A table can have many Super Keys.

E.g. of Super Key

1 ID 2 ID, Name3 ID, Address 4 ID, Department_ID

5 ID, Salary 6 Names, Address7 Names, Address, Department_ID So on as any combination which can identify the records

uniquely will be a Super Key.

(II) Candidate Key :It can be defined as minimal Super Key or irreducible Super Key. In other words an

attribute or a combination of attribute that identifies the record uniquely but none of its proper subsets can

identify the records uniquely.E.g. of Candidate Key

1 Code 2 Names, Address

For above table we have only two Candidate Keys (i.e. Irreducible Super Key) used to identify the recordsfrom the table uniquely. Code Key can identify the record uniquely and similarly combination of Name and

Address can identify the record uniquely, but neither Name nor Address can be used to identify the recordsuniquely as it might be possible that we have two employees with similar name or two employees from thesame house.

(III) Primary Key-:

A Candidate Key that is used by the database designer for unique identification of eachrow in a table is known as Primary Key. A Primary Key can consist of one or more attributes of a table. E.g. ofPrimary Key - Database designer can use one of the Candidate Key as a Primary Key. In this case we have

Code and Name, Address as Candidate Key, we will consider Code Key as a Primary Key as the other

key is the combination of more than one attribute.

(IV) Foreign Key :A foreign key is an attribute or combination of attribute in one base table that points to the

candidate key (generally it is the primary key) of another table. The purpose of the foreign key is to ensure

referential integrity of the data i.e. only values that are supposed to appear in the database are permitted.

E.g. of Foreign Key Let consider we have another table i.e. Department Table with AttributesDepartment_ID, Department_Name, Manager_ID, Location_ID with Department_ID as an Primary

Key. Now the Department_ID attribute of Employee Table (dependent or child table) can be defined as theForeign Key as it can reference to the Department_ID attribute of the Departments table (the referenced or

parent table), a Foreign Key value must match an existing value in the parent table or be NULL.



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(V) Composite Key:If we use multiple attributes to create a Primary Key then that Primary Key is called

Composite Key (also called a Compound Key or Concatenated Key). E.g. of Composite Key, if we have used

Name, Address as a Primary Key then it will be our Composite Key.

(VI) Alternate Key:Alternate Key can be any of the Candidate Keys except for the Primary Key. E.g. of

Alternate Key is Name, Address as it is the only other Candidate Key which is not a Primary Key.(VII) Secondary Key:

The attributes that are not even the Super Key but can be still used for identification

of records (not unique) are known as Secondary Key. E.g. of Secondary Key can be Name, Address, Salary,Department_ID etc. as they can identify the records but they might not be unique.

SQL Commands- :SQL have the different type of commands that are given below -

1. DDL (Data Definition Language)-:A data base schema is specifies by a set of definitions expressed

by a special language called DDL. Example of DDL commands are given below-:

CREATE- to create objects in the database. ALTER- alters the structure of the database. DROP- delete objects from the database.

TRUNCATE- remove all records from a table, including all spaces allocated for the recordsare removed. COMMENT- add comments to the data dictionary. RENAME- rename an object.

2. DML (Data Manipulation Language)-: This language that enable user to access or manipulate data

as organized by appropriate data model. Procedural DML or Low level: DML requires a user tospecify what data are needed and how to get those data. Non-Procedural DML or High level: DML

requires a user to specify what data are needed without specifying how to get those data.

SELECT - retrieve data from the a database INSERT - insert data into a table UPDATE - updates existing data within a table DELETE - deletes all records from a table, the space for the records remain MERGE- UPSERT operation (insert or update)

CALL- call a PL/SQL or Java subprogram EXPLAIN PLAN - explain access path to data LOCK TABLE - control concurrency

3. DCL-:Data Control Language (DCL) statements. Some examples:

GRANT -gives user's access privileges to database REVOKE- withdraw access privileges given with the GRANT command

4. TCL-: Transaction Control (TCL) statements are used to manage the changes made by DML

statements. It allows statements to be grouped together into logical transactions.

COMMIT -save work done SAVEPOINT -identify a point in a transaction to which you can later roll back ROLLBACK -restore database to original since the last COMMIT SET TRANSACTION - Change transaction options like isolation level and what rollback

segment to use

5. VDL (View Definition Language) -: It specifies user views and their mappings to the conceptualschema.

6. SDL (Storage Definition Language)-: This language is to specify the internal schema. This language

may specify the mapping between two schemas.

Data dictionary-:A data dictionary is a collection of descriptions of the data objects or items in a data model

for the benefit of programmers and others who need to refer to them. A first step in analyzing a system ofobjects with which users interact is to identify each object and its relationship to other objects. This process is

called data modeling and results in a picture of object relationships. After each data object or item is given a



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descriptive name, its relationship is described (or it becomes part of some structure that implicitly describesrelationship), the type of data (such as text or image or binary value) is described, possible predefined valuesare listed, and a brief textual description is provided. This collection can be organized for reference into a book

called a data dictionary.

ER model-:The ER model defines the conceptual view of a database. It works around real-world entities and

the associations among them. At view level, the ER model is considered a good option for designing databases.Entity-:

An entity can be a real-world object, either

animate or inanimate, that can be easily identifiable. Forexample, in a school database, students, teachers, classes,

and courses offered can be considered as entities. All theseentities have some attributes or properties that give them their identity.

Entity set-:An entity set is a collection of similar types of entities. An entity set may contain entities with

attribute sharing similar values. For example, a Students set may contain all the students of a school; likewise a

Teachers set may contain all the teachers of a school from all faculties. Entity sets need not be disjoint.

Attributes-:

Entities are represented by means of their properties, called attributes. All attributes have values.For example, a student entity may have name, class, and age as attributes. There are different type of attributes

that are given below-

1. Simple attribute:Simple attributes are atomic values, which cannot be divided further. For example, a

student's phone number is an atomic value of 10 digits.

2. Composite attribute:Composite attributes are made of more than one simple attribute. For example, a

student's complete name may have first_name and last_name.

3. Derived attribute :Derived attributes are the attributes that do not exist in the physical database, but

their values are derived from other attributes present in the database. For example, average_salary in adepartment should not be saved directly in the database, instead it can be derived. For another example, age

can be derived from data_of_birth.4. Single-value attribute:

Single-value attributes contain single value. For example

Social_Security_Number.

5. Multi-value attribute:Multi-value attributes may contain more than one values. For example, a person

can have more than one phone number, email_address, etc.

Generalization-:

As mentioned above, the process of generalizing entities,

where the generalized entities contain the properties of all the generalizedentities is called generalization. In generalization, a number of entitiesare brought together into one generalized entity based on their similar

characteristics. For example, pigeon, house sparrow, crow and dove canall be generalized as Birds.

Specialization-:

Specialization is the opposite of generalization. In specialization, a group of entities is

divided into sub-groups based on their characteristics. Take a group Person for example. Aperson has name, date of birth, gender, etc. These properties are common in all persons,

human beings. But in a company, persons can be identified as employee, employer,



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customer, or vendor, based on what role they play in the company. Similarly, in a school database, persons canbe specialized as teacher, student, or a staff, based on what role they play in school as entities.

Normalization-:

If a database design is not perfect, it may contain anomalies, which are like a bad dream for any

database administrator. Managing a database with anomalies is next to impossible.

Update anomalies:If data items are scattered and are not linked to each other properly, then it could lead to

strange situations. For example, when we try to update one data item having its copies scattered over severalplaces, a few instances get updated properly while a few others are left with old values. Such instances leave

the database in an inconsistent state.

Deletion anomalies-:We tried to delete a record, but parts of it was left undeleted because of unawareness,

the data is also saved somewhere else.Insert anomalies-:

We tried to insert data in a record that does not exist at all. Normalization is a method to

remove all these anomalies and bring the database to a consistent state.

First Normal Form-:First Normal Form is defined in the definition of relations (tables) itself. This rule defines

that all the attributes in a relation must have atomic domains. The values in an atomic domain are indivisible

units. We re-arrange the relation (table) as below, to convert it to First Normal Form.

Each attribute must contain only a single value from its pre-defined domain.

Second Normal Form-:Before we learn about the second normal form, we need to understand the following

1. Prime attribute : An attribute, which is a part of the prime-key, is known as a prime attribute.

2. Non-prime attribute: An attribute, which is not a part of the prime-key, is said to be a non-primeattribute. If we follow second normal form, then every non-prime attribute should be fully functionally

dependent on prime key attribute. That is, if X A holds, then there should not be any proper subset Y of X,

for which Y A also holds true. We see here in Student_Project relation that the prime key attributes areStu_ID and Proj_ID. According to the rule, non-key attributes, i.e. Stu_Name and Proj_Name must be

dependent upon both and not on any of the prime key attribute individually. But we find that Stu_Name can be

identified by Stu_ID and Proj_Name can be identified by Proj_ID independently. This is called partialdependency, which is not allowed in Second Normal Form. We broke the relation in two as depicted in the

above picture. So there exists no partial dependency.



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Third Normal Form-:For a relation to be in Third Normal Form, it must be in Second Normal form and the

following must satisfy No non-prime attribute is transitively dependent on prime key attribute. For any non-

trivial functional dependency, X A, then either X is a super key or, A is prime attribute. We find that inthe above Student_detail relation, Stu_ID is the key and only prime key attribute. We find that City can be

identified by Stu_ID as well as Zip itself. Neither Zip is a super key nor is City a prime attribute. Additionally,

Stu_ID Zip City, so there exists transitive dependency. To bring this relation into third normal form, webreak the relation into two relations as follows-

Boyce-Codd Normal Form-: Boyce-Codd Normal Form (BCNF) is an extension of Third Normal Form on

strict terms. BCNF states that For any non-trivial functional dependency, X A, X must be a super-key. Inthe above image, Stu_ID is the super-key in the relation Student_Detail and Zip is the super-key in the relation

ZipCodes. So, Stu_ID Stu_Name, Zip and Zip City which confirms that both the relations are in BCNF.

ACID Properties-:

A transaction is a very small unit of a program and it may contain several low level tasks. Atransaction in a database system must maintain Atomicity, Consistency, Isolation, and Durability commonly known as ACID properties in order to ensure accuracy, completeness, and data integrity.

Atomicity This property states that a transaction must be treated as an atomic unit, that is, either all

of its operations are executed or none. There must be no state in a database where a transaction is left

partially completed. States should be defined either before the execution of the transaction or afterthe execution/abortion/failure of the transaction.

Consistency The database must remain in a consistent state after any transaction. No transactionshould have any adverse effect on the data residing in the database. If the database was in a

consistent state before the execution of a transaction, it must remain consistent after the execution ofthe transaction as well.

Durability The database should be durable enough to hold all its latest updates even if the system

fails or restarts. If a transaction updates a chunk of data in a database and commits, then the databasewill hold the modified data. If a transaction commits but the system fails before the data could be

written on to the disk, then that data will be updated once the system springs back into action.

Isolation In a database system where more than one transaction are being executed simultaneouslyand in parallel, the property of isolation states that all the transactions will be carried out andexecuted as if it is the only transaction in the system. No transaction will affect the existence of any

other transaction.

OLAP-:On Line Analytical Processing (OLAP) is a Business Intelligence (BI) reporting system. OLAP

provides the user with the capability to sum, count, average and do other simple arithmetic operations ongroups of data. An OLAP report has measures and dimensions. Measures are the data values to be displayed.



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Dimensions are characteristics of the measures. OLAP reports are called OLAP cubes, although such reportsare not limited to three dimensions.

ODBC-:

ODBC is a standard that contains an interface that provides a common language for applicationprograms to access and process SQL databases. In order to use ODBC, a driver, server name, database name,user id, and password are required. ODBC is important for Internet applications and has gained wide

acceptance.

ODBC- :

ODBC is a standard that contains an interface that provides a common language for applicationprograms to access and process SQL databases. In order to use ODBC, a driver, server name, database name,user id, and password are required. ODBC is important for Internet applications and has gained wide

acceptance.

Entity-:It is a 'thing' in the real world with an independent existence.

Entity type-:

It is a collection (set) of entities that have same attributes.

Entity set-:

It is a collection of all entities of particular entity type in the database.

Weak Entity set-:An entity set may not have sufficient attributes to form a primary key, and its primary key

compromises of its partial key and primary key of its parent entity, then it is said to be Weak Entity set.

Database Trigger-:A database trigger is a PL/SQL block that can defined to automatically execute for insert,

update, and delete statements against a table. The trigger can e defined to execute once for the entire statement

or once for every row that is inserted, updated, or deleted. For any one table, there are twelve events for whichyou can define database triggers. A database trigger can call database procedures that are also written in

PL/SQL.

Cold backup and hot backup (in case of Oracle)-:

Cold Backup-:

It is copying the three sets of files (database files, redo logs, and control file) when the instanceis shut down. This is a straight file copy, usually from the disk directly to tape. You must shut down the

instance to guarantee a consistent copy. If a cold backup is performed, the only option available in the event ofdata file loss is restoring all the files from the latest backup. All work performed on the database since the last

backup is lost.

Hot Backup-:Some sites (such as worldwide airline reservations systems) cannot shut down the database

while making a backup copy of the files. The cold backup is not an available option.

SQL view-:A SQL view is a virtual table built from other tables or views. Views are used to

(1) Hide columns or rows,

(2) show the results of computed columns,(3) Hide complicated SQL syntax,

(4) Layer built-in functions,(5) provide a level of indirection between application programs and tables,(6) Assign different sets of processing permissions to tables, and(7) To assign different sets of triggers to the same table.

What is Trigger-:A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE or

UPDATE) occurs. Triggers are Stored in and managed by the DBMS. Triggers are used to maintain thereferential integrity of data by changing the data in a systematic fashion. A trigger cannot be called or

executed; DBMS automatically fires the trigger as a result of a data modification to the associated table.



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Triggers can be viewed as similar to stored procedures in that both consist of procedural logic that is stored atthe database level. Stored procedures, however, are not event-drive and are not attached to a specific table astriggers are. Stored procedures are explicitly executed by invoking a CALL to the procedure while triggers are

implicitly executed. In addition, triggers can also execute stored procedures.

What is Cursor-:Cursor is a database object used by applications to manipulate data in a set on a row-by- row

basis, instead of the typical SQL commands that operate on all the rows in the set at one time.In order to work with a cursor we need to perform some steps in the following order:

1. Declare cursor2. Open cursor3. Fetch row from the cursor4. Process fetched row5. Close cursor6. Deallocate cursor

Different Types of Join-:Cross Join a cross join that does not have a WHERE clause produces the Cartesian

product of the tables involved in the join. The size of a Cartesian product result set is the number of rows in the

first table multiplied by the number of rows in the second table. The common example is when company wants

to combine each product with a pricing table to analyze each product at each price.

Inner Join-A join that displays only the rows that have a match in both joined tables is known as inner Join.This is the default type of join in the Query and View Designer.

Outer Join- A join that includes rows even if they do not have related rows in the joined table is an OuterJoin. You can create three different outer join to specify the unmatched rows to be included:

Left Outer Join- In Left Outer Join all rows in the first-named table i.e. "left" table, which appears leftmost inthe JOIN clause are included. Unmatched rows in the right table do not appear.

Right Outer Join-In Right Outer Join all rows in the second-named table i.e. "right" table, which appearsrightmost in the JOIN clause are included. Unmatched rows in the left table are not included.

Full Outer Join- In Full Outer Join all rows in all joined tables are included, whether they are matched or not.

Self Join-This is a particular case when one table joins to itself, with one or two aliases to avoid confusion. A

self join can be of any type, as long as the joined tables are the same. A self join is rather unique in that itinvolves a relationship with only one table. The common example is when company has a hierarchal reportingstructure whereby one member of staff reports to another. Self Join can be Outer Join or Inner Join.

Data Warehousing-:

Subject-oriented, meaning that the data in the database is organized so that all the dataelements relating to the same real world event or object are linked together; Time-variant, meaning that the

changes to the data in the database are tracked and recorded so that reports can be produced showing changes

over time; Non-volatile, meaning that data in the database is never over-written or deleted, once committed,the data is static, read-only, but retained for future reporting. Integrated, meaning that the database contains

data from most or all of an organization's operational applications, and that this data is made consistent.



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DATA STRUCTURE-:In computer science, a data structure is a particular way of storing and organizing

data in a computers memory so that it can be used efficiently. Data may be organized in many different ways;

the logical or mathematical model of a particular organization of data is called a data structure. The choice of aparticular data model depends on the two considerations first; it must be rich enough in structure to mirror the

actual relationships of the data in the real world. On the other hand, the structure should be simple enough that

one can effectively process the data whenever necessary.

Need of data structure-: It gives different level of organization data. It tells how data can be stored and accessed in its elementary level.Provide operation on group of data, such as adding an item, looking up highest priority item.Provide a means to manage huge amount of data efficiently.Provide fast searching and sorting of data.

Selecting a data structure-:Selection of suitable data structure involve following steps

Analyze the problem to determine the resource constraints a solution must meet.Determine basic operation that must be supported. Quantify resource constraint for each operation

Select the data structure that best meets these requirements.Each data structure has cost and benefits. Rarely is one data structure better than other in all situations.

Type of data structure-:1. Static data structure: A data structure whose organizational characteristics are invariant throughout itslifetime. Such structures are well supported by high-level languages and familiar examples are arrays and

records. The prime features of static structures are

[A]None of the structural information need be stored explicitly within the elements it is often held in adistinct logical/physical header;

[B]The elements of an allocated structure are physically contiguous, held in a single segment of memory.

[C]All descriptive information, other than the physical location of the allocated structure, is determined by thestructure definition.

[D]Relationships between elements do not change during the lifetime of the structure.2. Dynamic data structure-:

A data structure whose organizational characteristics may change during its

lifetime. The adaptability afforded by such structures, e.g. linked lists, is often at the expense of decreased

efficiency in accessing elements of the structure. Two main features distinguish dynamic structures from staticdata structures. Firstly, it is no longer possible to infer all structural information from a header; each data

element will have to contain information relating it logically to other elements of the structure. Secondly, usinga single block of contiguous storage is often not appropriate, and hence it is necessary to provide some storage

management scheme at run-time.

Linear Data Structure-:

A data structure is said to be linear if its elements from any sequence. There are

basically two ways of representing such linear structure in memory.

a) One way is to have the linear relationships between the elements represented by means of sequentialmemory location. These linear structures are called arrays.b) The other way is to have the linear relationship between the elements represented by means of pointers orlinks. These linear structures are called linked lists. The common examples of linear data structure are arrays,

queues, stacks and linked lists.

Non-linear Data Structure-:This structure is mainly used to represent data containing a hierarchical

relationship between elements. E.g. graphs, family trees and table of contents.

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Array-:The simplest type of data structure is a linear (or one dimensional) array. A list of a finite number n of

similar data referenced respectively by a set of n consecutive numbers, usually 1, 2, 3 . . . . . . . n. if we choose

the name A for the array, then the elements of A are denoted by subscript notation.

Linked List-:A linked list or one way list is a linear collection of data elements, called nodes, where the linear

order is given by means of pointers. Each node is divided into two parts:1.The first part contains the information of the element/node

2.The second part contains the address of the next node (link /next pointer field) in the list.

There is a special pointer Start/List contains the address of first node in the list. If this special pointer containsnull, means that List is empty.

Abstract Data Type-:It can be defined as a collection of data items together with the operations on the data.

The word abstract refers to the fact that the data and the basic operations defined on it are being studied

independently of how they are implemented. It involves what can be done with the data, not howhas to bedone. For ex, in the below figure the user would be involved in checking that what can be done with the data

collected not how it has to be done.

Queue- :

A queue is a linear list of elements inwhich deletion can take place only at one end,

called the front, and insertions can take place onlyat the other end, called the rear. The term front

and rear are used in describing a linear list only

when it is implemented as a queue. Queue is alsocalled first-in-first-out (FIFO) lists. Since the first

element in a queue will be the first element out of

the queue. In other words, the order in which elements enters a queue is the order in which they leave.

There are main two ways to implement a queue:1. Circular queue using array

2. Linked Structures (Pointers)

Primary queue operations:

Enqueue : insert an element at the rear of the queue.Dequeue : remove an element from the front of the queue Following is the algorithm which describes theimplementation of Queue using an Array.

Priority queue-:

Priority queue is a linear data structure. It is having a list of items in which each item hasassociated priority. It works on a principle add an element to the queue with an associated priority and remove

the element from the queue that has the highest priority. In general different items may have differentpriorities. In this queue highest or the lowest priority item are inserted in random order. It is possible to delete

an element from a priority queue in order of their priorities starting with the highest priority. While priority

queues are often implemented with heaps, they areconceptually distinct from heaps. A priority queue is an

abstract concept like "a list" or "a map"; just as a list can be

implemented with a linked list or an array, a priority queue

can be implemented with a heap or a variety of othermethods such as an unordered array.

Stack-:It is an ordered group of homogeneous items of

elements. Elements are added to and removed from the top

of the stack (the most recently added items are at the top ofthe stack). The last element to be added is the first to be

removed (LIFO: Last In, First Out).



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Stack Operations-:These are two basic operations associated with stack:

1. Push() is the term used to insert/add an element into a stack.

2. Pop() is the term used to delete/remove an element from a stack.

Tree - :A node is a structure which may contain a value, a condition, or represent a separate data structure

(which could be a tree of its own). Each node in a tree has zero or more child nodes, which are below it in thetree (by convention, trees grow down, not up as they do in nature). A node that has a child is called the child's

parent node (or ancestor node, or superior). A node has at most one parent. Nodes that do not have any

children are called leaf nodes. They are also referred to as terminal nodes. The height of a node is the lengthof the longest downward path to a leaf from that node. The height of the root is the height of the tree. The

depth of a node is the length of the path to its root (i.e., its root path).

Binary Tree -:

The binary tree is a fundamental data structure

used in computer science. The binary tree is a useful datastructure for rapidly storing sorted data and rapidly retrieving

stored data. A binary tree is composed of parent nodes, or

leaves, each of which stores data and also links to up to two

other child nodes (leaves) which can be visualized spatially asbelow the first node with one placed to the left and with one

placed to the right. It is the relationship between the leaveslinked to and the linking leaf, also known as the parent node,

which makes the binary tree such an efficient data structure. It is

the leaf on the left which has a lesser key value (i.e, the valueused to search for a leaf in the tree), and it is the leaf on the rightwhich has an equal or greater key value. As a result, the leaves

on the farthest left of the tree have the lowest values, whereasthe leaves on the right of the tree have the greatest values. Moreimportantly, as each leaf connects to two other leaves, it is the beginning of a new, smaller, binary tree. Due to

this nature, it is possible to easily access and insert data in a binary tree using search and insert functionsrecursively called on successive leaves.

Complete Binary Tree -:A binary tree T with n levels is complete

if all levels except possibly the last are completely full, and the last

level has all its nodes to the left side. A complete binary tree has 2knodes at every depth k < n and between 2n and 2n+1-1 nodesaltogether. It can be efficiently implemented as an array, where a

node at index i has children at indexes 2i and 2i+1 and a parent at

index i/2, with one-based indexing. If child index is greater than thenumber of nodes, the child does not exist. A complete binary tree

can be represented in an array in the following approach. If root

node is stored at index i, its left, and right children are stored atindices 2*i+1, 2*i+2 respectively.

Traversal:-A traversal is a process that visits all the nodes in the tree. Since a tree

is a nonlinear data structure, there is no unique traversal.

There are three different types traversals,

PreOrder traversal -visit the parent first and then left and right children. InOrder traversal - visit the left child, then the parent and the right child. PostOrder traversal -visit left child, then the right child and then the parent.

There is only one kind of breadth-first traversal--the level order traversal.



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This traversal visits nodes by levels from top to bottom and from left to right. As an example consider thefollowing tree and its four traversals:PreOrder - 8, 5, 9, 7, 1, 12, 2, 4, 11, 3

InOrder - 9, 5, 1, 7, 2, 12, 8, 4, 3,11PostOrder - 9, 1, 2, 12, 7, 5, 3, 11,4, 8In the next picture we demonstrate the order of node visitation. Number 1 denotes the first node in a particular

traversal and 7 denote the last node.

Binary Search Tree-:We consider a particular kind of a binary tree called

a Binary Search Tree (BST). The basic idea behind this data structure is to

have such a storing repository that provides the efficient way of data sorting,searching and retrieving. A BST is a binary tree where nodes are ordered in

the following way:

Each node contains one key (also known as data)The keys in the left subtree are less then the key in its parent node, in short

L < P.

The keys in the right subtree are greater the key in its parent node, in short P < R.

Duplicate keys are not allowed.In the following tree all nodes in the left subtree of 10 have keys < 10 while all nodes in the right subtree > 10.Because both the left and right subtrees of a BST are again search trees; the above definition is recursively

applied to all internal nodes:

Heaps-:A heap is a binary tree where the elements are arranged in a certain order proceeding from smaller to

larger. In this way, a heap is similar to a binary search tree (discussed previously), But the arrangement of theelements in a heap follows rules that are different from a binary search tree:1. In a heap, the element contained by each node is greater than or equal to the elements of that node's children.

2. The tree is a complete binary tree, so that every level except the deepest must contain as many nodes aspossible and at the deepest level, all the nodes are as far left as possible.

Linear Search-:Linear search or sequential search is a method for finding a particular value in a list that consistsof checking every one of its elements, one at a time and in sequence, until the desired one is found.

Binary search-:A binary search or half-interval search algorithm finds the position of a specified input value

(the search "key") within an array sorted by key value. For binary search, the array should be arranged in

ascending or descending order. In each step, the algorithm compares the search key value with the key value ofthe middle element of the array. If the keys match, then a matching element has been found and its index is



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returned. Otherwise, if the search key is less than the middle element's key, then the algorithm repeats itsaction on the sub-array to the left of the middle element or, if the search key is greater, on the sub-array to theright. If the remaining array to be searched is empty, then the key cannot be found in the array and a special

"not found" indication is returned.

Graph-:Data sometimes contains a relationship between

pairs of elements which is not necessarily hierarchical innature, e.g. an airline flights only between the cities

connected by lines. This data structure is called Graph.

Graph representation: a graph is a collection of vertices

(or nodes), pairs of which are joined by edges (or lines).

Graph operations and representation-:

1. Path problems: Since a graph may have more than one path between two vertices, we may be interestedin finding a path with a particular property. For example, find a path with the minimum length from the

root to a given vertex (node).

2. Simple path: a path in which all vertices, except possibly the first and last, are different.

3. Undirected graph: a graph whose vertices do not specify a specific direction.4. Directed graph: a graph whose vertices do specify a specific direction.

5. Connected graph: there is at least one path between everypair of vertices.

6. Bipartite graphs: graphs that have vertexes that are partitioned into 2 subsets A and B, where every edge

has one endpoint in subset A and the other endpoint in subset B.

7. A complete graph: an n-vertex undirected graph with n(n-1)/2 edges is a complete graph.

8. A complete digraph: (denoted as Kn) for n-vertices a complete digraph contains exactly n(n-1) directed

edges

9. Incident: the edge (i, j) is incident on the vertices i and j (there is a path between i and j)

10. In-degree: the in-degree d of vertex i is the # of edges incident to i (the # of edges coming into this vertex)

11. The out-degree: the out-degree d of vertex i is the # of edges incident from vertex i (the # of edgesleaving vertex i)

12. The degree of a vertex: the degree d of vertex i of an undirected graph is the number of edges incident on

vertex i13. Connected component: a maximal sub-graph that is connected, but you cannot add vertices and edges

from the original graph and retain connectedness. A connected graph has EXACTLY one component

14. Communication network: Each edge is a feasible link that can be constructed. Find the components andcr

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