Database

A Database is a collection of related data that is organized so that can be easily accessed, managed and
updated. 

Database system

 A Database system is basically a computer-based record-keeping system. 

DBMS  

DBMS stands for a database management system. The database is managed by some special software packages known as a database management system (DBMS). DBMS is specially designed software to create a connection between user and program and to store data in an organized manner. The purpose of DBMS software is to allow the user to create, modify, and maintain database.

Example: MS Access, My SQL, Oracle, etc.

  

 

 

HTML(Hypertext Markup Language)

HTML is the language that helps in creating and designing web content. It is a markup language. It has a
collection of tags and attributes for defining the layout and structure of the web page. A HTML document has the extension .htm or .html.

XML (EXtensible Markup Language)

XML is a markup language like HTML. It is designed to carry or store data. Unlike HTML, it does not have predefined tags. It is possible to define new tags
in XML.

WWW (World Wide Web) 

The World Wide Web was invented by a British scientist, Tim Berners-Lee in 1989. World Wide Web, which is also known as a Web, is the universe of the information available on the internet. It is a collection of websites or web pages stored in web servers and connected to local computers through the internet. These websites contain text pages, digital images, audios, videos, etc. Users can access the content of these sites from any part of the world over the internet using their devices such as computers, laptops, cell phones, etc.

Web page 

A web page is an electronic document designed using HTML. It displays information in textual or graphical form. It may also contain downloadable data files, audio files, or video files. Traversal from one webpage to another web page is possible through hyperlinks. 

A web page can be classified into two types:

1. Static web page: A web page that displays the same kind of information whenever a user visits it, is known as a Static web page.
   
   
2. Dynamic web page: A web page that displays different information each time whenever a user visits it, is known as Dynamic web page.

 Website

A collection of web pages that are accessible through a single domain known as a website. A website has multiple webpages providing information about a particular entity.

Web Browser

A web browser is a software program to navigate the web pages on the internet. A browser interprets the coding language of the web page and displays it in graphic form. A web browser allows anyone to access the web without even knowing commands used in software languages to design a web page.  

Internet works on the client-server model. A web browser is a client that requests the information from the web server. The web server sends the information back to the client. The web address of the webpage written on the address bar tells the web browser which page to access.

Web Server

A web server is a WWW server that responds to the requests made by web browsers/clients.

URL (Uniform resource locator) 

The web address of the web page written on the address bar of the browser is known as the uniform resource locator (URL). A URL is a formatted text string used to identify a network resource on the Internet.
Network resources are files that can be plain Web pages, text documents, graphics, downloadable files,
services, or programs. Every network resource on the web has a unique URL. 

Domain Name  

A server identified by a set of characters known as Domain name. It is an address part of any URL from which we access all resources available on that server.

Web Hosting

Web hosting is the process of uploading/saving the web content on a web server to make it available on
WWW. In case an individual or a company wants to make its website available on the internet, it should be hosted on a web server.

 

Network Security Concept

Network security is an important part of any network. It protects data when transmitting from one computer to another. Some terms related to network security are explained below:

Virus

A virus is a computer program that is made to harm our computer data, files, and other programs. Viruses can spread computers to computer and they can replicate themselves.

Antivirus

Antivirus is a computer program that used to find viruses in computers. Antivirus can disinfect virus-infected files and if it is not able to disinfect then it deleted the file. It is a very important program for every computer to make computers and networks more secure.

Spam

Spam is a mail or message that is sent to users without their approval. It can be sent by any organization to thousands or millions of people for promoting a particular product or service. It also can be a mail scam to get other people's money.

Cookies

A cookie is a small text file that any browser store to keep track of a user's activity on a specific website. It also used to identify the user or customize webpages according to the user's interests.

Firewall

A firewall is a network security device that monitors incoming and outgoing network traffic. It establishes a barrier between our internal network and incoming traffic from external sources (such as the internet) to block malicious traffic like viruses and hackers. A firewall can be either hardware and software.

HTTPS

HTTPS stands for HyperText Transfer Protocol Secure. It is a secure version of HTTP. It is a protocol for securing the communication between two systems e.g. the browser and the webserver. In HTTPS, the communication protocol is encrypted using Transport Layer Security (TLS) or, Secure Sockets Layer (SSL). 

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SIM  (Subscriber Identity Module)

 A sim is a tinny computer cheap card that gives a cellular device its unique phone number.  It contains all the credentials which important to connect to any cellular network. Current SIMs typically have 16 to 64 kb of memory which used for storing personal phone numbers, text messages, and other data.

SMS  (Short Message Service)

SMS is the transmission of short text messages to and from a mobile phone, fax machine, and other devices. The message must be no longer than some fixed number of alphanumeric characters and contain no images or graphics.

MMS  (Multimedia Message Service)

It is a standard messaging service to send multimedia content to and from any mobile phone over Cellular network. This includes images, videos, and sound files.

E-mail  (Electronic mail)

It allows you to send and receive messages to and from anyone with an email address anywhere in the world. Email address is a unique address for every user, required to receive and send emails. Photos documents and other files can be attached to an email so that more information can be shared.

Voicemail

A Voicemail system is a Computer Based system that allows users and subscribers to exchange personal voice messages.

Video Conferencing

A technology that allows users in different locations to hold face to face meetings without having to move to a single location.

Chat

Online textual talk in real-time is called chatting. In chatting we type a message on our screen, which is immediately received by the recipient then the recipient can type a message in response to our message which is received by us instantly.

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Wi-Fi

Wi-Fi is a wireless networking technology that allows computers to connect with the internet without using direct lines or cable from our PC to the Internet. For working of wi-fi we need-

1. Internet Connection
2. Wireless Router
3. Computers having a wireless network card.

Wi-Fi Hotspot

Wi-Fi is a venue or place that provides Wi-Fi access. These locations can be School campus, Restaurant, Library, Railay station, etc where the public can use a laptop, Mobile phone, or another suitable device to access Wi-Fi.

WiMax

WiMax is a wireless digital communication system. WiMax can provide broadband wireless access up to 30 miles (50 KM) for fixed stations. WiMax requires a  tower called base station similar to a cell phone tower. WiMax is more secure, can cover more area, and can provide more internet speed than a Wi-Fi.

VOIP

VOIP stands for Voice over Internet Protocol. VOIP provides phone services over the internet. It is more reliable and cheaper than traditional phone services.

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1G mobile system

The 1G mobile system is introduced in the early 1980s. The 1G mobile system was based on analog cellular Technology. This network was mainly designed for voice calls no consideration of Data Services. The major drawback of the 1G system were its low capacity, poor voice links and no security.

2G mobile system

The 2G network was the first digital cellular system introduced in 1990. The 2G system was based on GSM Technology. 2G was offering improved sound quality, better security, SMS, Voicemail and fax services.

2.5G mobile system

 It is the enhanced version of 2G. It offers services like MMS, sending pictures through email.

3G mobile system

3G Technology adds multimedia facilities to the 2G phone by allowing video, audio and graphics applications. With the invention of 3G watching online videos and video conferencing become a reality. It has the capacity of higher data rates and it opens the door to many internet style applications. The 3G mobile system is also known as the universal mobile telecommunication system (UMTS).

4G mobile system

4G is an enhanced version of 3G it is based on packet switching. It is able to support faster transmission. It provides data rate up to 100 MBPS. It is wireless access technology.

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WLL

WLL stands for wireless local loop and it is basically used to provide a telephone connection to the home. WLL is used for wireless communication links that deliver telephonic services or broadband services to customers it is mostly used in developing countries where cable infrastructure is either expensive or speed is not fast. In other words, WLL is a system that connects subscribers to the public switched Telephone Network (PSTN) using radio signals as a substitute for other connecting media.

GPRS

GPRS stands for General Packet Radio Service. GPRS is used for wireless communication using a mobile device with this service you can access the internet, sends emails, and so on.

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Wireless Communication

Wireless communication means the method of transferring information between computing devices without using any physical connection. For example- when we try to access any agency database server from our mobile phone without using any physical connection. Not all wireless technologies are mobile technology.  In wireless communication device is continuously connected to the base network.

Mobile Communication

Mobile is a device that is portable. Mobile communication is based on a cellular network. A cellular network is nothing but a radio network. A mobile device may be a PDA, smartphone, laptop, and any other device that allows the user to complete computing tasks without connection with any other wireless network. In this communication, the device is not continuously connected to the base or central network.

Mobile Communication Technologies

GSM: GSM stands for a global system for mobile communication which is one of the leading digital cellular systems. The GSM standard for Digital cell phones was established in Europe in the mid 9080s. It becomes the International standard in Europe, Australia, and much of Asia and Africa. Cell phones users can buy one phone that will work anywhere where the standard is supported. To connect to the specific service providers in different countries, GSM users simply switch SIM cards. They stores all the connections and identification numbers to access a particular wireless service provider.

CDMA: CDMA stands for code division multiple access. CDMA is designed by Qualcomm in the United States. It is used second and third generation of the wireless communication. It is a digital cellular technology that uses spread spectrum techniques. Because of spread spectrum  is it it maintains high security and noise reduction. In this techniques several transmitters can send information simultaneously over a single communication channel.

Network Protocol / Communication Protocol

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In information technology, a protocol is the special set of rules that two or More computer on a network follows to communicate with each other. A protocol defines how computers identify one another on a network and how this information reaches its Final Destination.  A protocol is needs every time we want to perform any task on the network. It may be transferring data or taking a printout on a network printer for accessing the central database. Each network uses different protocols.

Hypertext: Hypertext is the text that is specially coded using a standard coding language called HTML which basically creates hyperlinks. These hyperlinks can be text, graphics, image, sound, and videos that are used to link users to some other file.

Some most common protocols are below:

HTTP

HTTP  is the protocol that is used for transferring hypertext between two computers and it is particularly used on the world wide web. HTTP is a TCP/IP based communication protocol and provides a standard for web browsers and servers to communicate. HTTP is based on the client-server principle. When a connection established between two computers the client computer sends the request to the server and server response to the request.

FTP (File Transfer Protocol)

This is the simplest and oldest protocol. It is designed for transferring files of any type (ASCII or binary) from one system to another on the internet. FTP is an application protocol that uses the internet's TCP/IP protocols. FTP based on the client-server principle. By giving the FTP command with any remote address we can send and receive files.

TCP/IP (Transmission Control Protocol / Internet Protocol)

TCP/IP are the two protocols that are used together and they form the backbone protocol of the internet. TCP/IP has two major components TCP and IP.

1. TCP: It breaks the data into packets that the network can handle efficiently. It manages the assembling of a message or file into smaller packets that are transmitted over the internet. It verifies all the packets when they arrived at the destination computer and then reassembles them in proper order. Data can be lost in the intermediate network, so TCP adds supports to detect errors or lost data and to Trigger transmission until the data is correctly and completely received.
2. IP: The internet protocol (IP) handles the address part of each packet so that it reaches the right destination. It gives a distinct address (called an IP address) to each data packet. It checks this address to see where to forward the message and finally they reassembled at the destination.

PPP (Point to Point Protocol)

PPP is a communication protocol used to establish a direct connection between nodes. It connects nodes without using any device or any host. It is used over phone lines and any other physical cable. It basically designed to help communication between two systems through telephone lines.

Telnet

Telnet is the main protocol for creating a connection with a remote machine. It allows us to connect with a remote computer over a TCP/IP network or internet. Once our Telnet client establishes a connection to the remote host our clients become a virtual terminal, allowing us to communicate with the remote host from our computer with whatever privileges you have been granted to the applications and data on the host computer.

SMTP (Simple Mail Transfer Protocol)

SMTP is a set of communication protocols that allow the software to transmit an e-mail over the internet. It is a program used for sending emails to other users based on e-mail addresses.

Types of Computer Network

A computer network means a group of networked computers. A network can be a small group of linked computers or can be a large group. Thus networks vary in size and complexity.  There can be four types of networks on the basis of geographical spread.

1. Personal area network (PAN)
2. Local area network (LAN)
3. Metropolitan area network (MAN)
4. Wide area network (WAN)

Personal area network (PAN)

A personal area network organized around an individual person, typically within a 10-metre range. For example- a person has a laptop, mobile phone, PDA and any portable printer all are connected with a single Wi-Fi network.

Local area network (LAN)

A local area network is a computer network that interconnects computer within a limited area such as Residency, School, laboratory, University campus, or office building.  The key purpose of a LAN  is to serve its user in resource sharing. The hardware, as well as software resources, are shared through LANs.

Metropolitan area network (MAN)

Metropolitan Area Network is the networks spread over a city.  For example -  cable TV Network that is spread over a city. It is just a bigger version of LAN and normally uses similar Technology. MAN is also the sharing of hardware and software resources along with its user.

Wide area network (WAN)

The network spread across the large geographical area like countries are known as wide area networks. A wide area network is a group of LANs that are spread across several locations and connected together to look like one big LAN.  Wide area network link offers computer to exchange information at laser costs and higher speeds. The internet is the largest WAN,  spanning the entire Earth.

Network Devices

For the efficient working of any network, many devices are required. Some of them are discussed below:

Modem (Modulator-Demodulator)

A modem is a Peripheral device that enables a computer to transmit data over telephone or cable lines. Because ordinary telephone lines cannot carry digital information, a modem changes digital data from our computer into analog data, a format that can be carried by telephone lines. Similarly, when modem receiving data then it changes analog data back into digital data.

HUB

A Hub is a hardware device used to connect several computers together. Basically, Hubs are multislot concentrators in which a number of computers can be plugged to grow the size of the network.

Hub can be either active and passive

1. Active Hub: Active hubs Electrically amplify the signal as it moves from one connected device to another.
2. Passive Hub: Passive hub allow the signals to pass from one computer to another without any change.

Switch

A switch is a device that is used to break a network into different sub-networks or the LAN  segment, this prevents traffic overloading on the network. in simple terms,  a network switch is a small hardware device that joins multiple computers together within one Local area network. Network switches appear nearly identical to a network hub, but a switch generally contains more intelligence than a hub. We can say that a switch is an intelligent hub and is obviously more expensive than a hub.

Gateway 

Gateway is a device that connects dissimilar networks. It is capable of joining together two networks that use different base protocols. It establishes an intelligent connection between local networks and external networks with completely different structures.

Ethernet Card

Ethernet is a LAN architecture developed by Xerox Corporation. Ethernet uses a Bus or star topology and can support Data transfer rates of up to 10 Mbps. In computer for use of ethernet have to install a special type of card called Ethernet card.

Ethernet card is a kind of network adaptor and is also known as a network interface card (NIC). It supports high-speed network connections via cables. Newer internet cards are installed usually by the manufacturer inside the computers.

RJ-45 Connector

 RJ-45 stands for registered Jack 45. RJ-45 is an 8 wire connector that is used to connect computers on a local area network (LAN) especially Ethernet

Bridge

A bridge is a network device that can connect two local networks with the same standard but a different type of cable. Bridges are capable to know which computers are on which side of the bridge, so they only allow those messages that going to cross the bridge.

Router

A router is a network device that works like a bridge but can handle different protocols. In short, A router is a network device that can connect two networks with different protocols.

Repeater

When a signal travels along a cable, it tends to lose strength. A repeater is a device that regenerates a network's signal and rebroadcasts it.

Wi-Fi Card

Wi-Fi is also known as WNIC (Wireless Network Interface Card). This is an essential component for the use of wi-fi. Without a wi-fi card, any computer can not be able to access wi-fi.

Satellites are an essential part of the telecommunication system worldwide today. They can carry a large amount of data. satellite communication is a special use of microwave transmission systems. A Satellite is placed above the earth where its orbital speed exactly matches the Earth's rotation speed.  Hence it always stays over the same point with respect to the Earth.  In satellite communication, the earth station consists of a satellite dish that functions as an antenna and communication equipment to transmit and receive data from satellite overhead.

Advantages of Satellite Transmission

1. The area coverage through satellite transmission is quite large.

2. This is particularly useful for sparsely populated areas.

Disadvantages of Satellite Transmission

1. Placing the satellite into its Orbit involves a very high cost.
2. Transmission is affected by weather conditions like rain, thunderstorm, etc.

Microwave signals are used to transmit data without the use of cables. The microwave signals are similar to radio and television signals. Microwaves are used for long-distance communication. In microwave communication parabolic antennas are mounted on towers to send data to other antennas.

Advantages of Microwave

1. It offers ease of communication over difficult terrain.
2. Microwaves have the ability to communicate over oceans.

Disadvantages of Microwave

1. It is an insecure communication.
2. Its propagation is susceptible to weather effects like rains, thunderstorms, etc.
3. Implementation and maintenance cost is high.
4. Bandwidth is limited.

We are quite familiar with Radios and their working. Each radio signal uses a different frequency and this differentiates it from others. The transmitter takes some message, encodes it, and then transmit it with the radio wave. The receiver on the other end receives the radio waves and decodes it. Both the transmitter and receiver use antennas to radiate and capture the radio signal. Radio transmission is widely used by delivery services, policemen, security personals, etc.

Advantages of Radio Wave

1. It is easy to communicate through radio waves in difficult terrains since there is no need for any type of cable.
2. It can travel long distances in all directions. Also they can easily pass through obstacles like buildings so it can be used anywhere.

 Disadvantages of Radio Wave

1. Data Transmission is not secure.
2. The radio wave is susceptible to weather effects like rains, thunderstorms, etc.

Infrared is a type of unguided or wired transmission media. This is the frequency of light that is not visible to the human eye. Infrared light is widely used for short-range communication. The remote control is used in TV, VCR, Stereos, and other devices all use infrared communication.

Advantages of Infrared

1. It having short-range communication hence it is a secure mode of transmission.
2. It is quite an inexpensive transmission medium.

Disadvantages of Infrared

1. It can be only used in short-range transmission.
2. Infrared wave transmission cannot pass through obstruction like walls, buildings, etc.

Optical Fiber

A Fiber Optic cable is a light pipe that is used to carry a light beam from one place to another. Optical fiber consists of thin strands of glass-like material. The light sources used are either light-emitting diodes (LEDs) or Laser diodes (LDs). The Fiber Optic Cable consists of three pieces-

1. Core - The glass or plastic through which the light travels.
2. Cladding - Cover of the core that reflects light back to the core.
3. Coating - It protects the fiber cable from a hostile environment.

Types of Optical Fiber Cable

There are two types of Optical Fiber Cable.

1. Single-node: It supports a segment length of up to 2 km and bandwidth of up to 100 Mbps.
2. Multi-node: It supports a segment length of up to 100 km and bandwidth of up to 2 Gbps.

Advantages of Optical Fiber

1. It is immune to electrical and magnetic Interface.
2. It is guaranteed secure transmission and has a very high transmission capacity.
3. It can be used for broadband.

Disadvantages of Optical Fiber

1. It is difficult to install and maintain since they are quite fragile.
2. It is most expensive in all the cables.
3. Connecting two fiber cable together is a difficult process.

Coaxial Cable

Coaxial cable is the most commonly used transmission media for LANs.  It consists of solid wire cores surrounded by one or more foil or wire shields, each separated by some kind of plastic insulator. The inner core carries the signal and the shield provides the ground. It has high electrical properties and is suitable for high-speed communication it is widely used for television signals and also in building security systems.

Coaxial Cable

Types of Coaxial Cable

1. Thicknet
2. Thinnet

Thicknet

Its cable segment can be up to 500 meters.

Thinnet

This is thinner than Thicknet. Its cable segment can be up to 185 meters.

Advantages of Coaxial Cable

1. Data transmission characteristics are better than twisted pair cable.

1.  It can be used for broadband communication.

2.  It can be used for a shared cable network.

3.  It offers a high bandwidth of up to 400 Mbps.

Disadvantages of Coaxial Cable

1. It is expensive compared to twisted pair cables.

2.  It is not compatible with twisted pair cable.

Transmission Media

Transmission media is a medium that carries a signal from one computer to another. It is also known as a communication channel. transmission media can be of two types:

1.  Guided Transmission Media (Wired Transmission Media)
2.  Unguided Transmission Media (Wireless Transmission Media)

Guided Transmission Media

This media physically connects the two or more computers. The data signal physically gets transferred from the source computer to the destination computer through the wired transmission medium.

Some of the Guided media are as follows: 

• Twisted pair cable
• Coaxial cable
• Optical Fiber

Unguided Transmission Media

Unguided or wireless transmission media transfer electromagnetic waves without using a physical conductor the signal is broadcasted through air or water.

Some of the Unguided media are as follows: 

• Infrared
• Radio Wave
• Microwave
• Satellite Link

Data Channel

A Data Channel is a medium used to carry data or information from one point to another point.

Baud

Baud is a unit of measurement for the information carrying capacity of a communication channel. The baud is synonymous with bps (bits per second).

1 Baud = 1 bps

Bandwidth

Bandwidth is the difference between the highest frequency signal component and the lowest frequency signal component. Frequency is measured in Hertz which is denoted by Hz. Hz can be also called Cycles per second.

1 Kilohertz (KHz) = 1000 Hz

1 Megahertz (MHz) = 1000 KHz

1 Gigahertz (GHz) = 1000 MHz

1 Terahertz (THz) = 1000 GHz

Data Transfer Rates

Data Transfer Rate is the speed with which data can transmit from one computer to another. This can be measure from, amount of data transferred per second by any device.

The data rate is measured in units of Bits per second (bps), Bytes per second (Bps), and Baud.

1 Byte = 8 bit

Bit based transfer rates

1000 bps = 1kbps

1000 kbps = 1 mbps

1000 mbps = 1 gbps

1000 gbps = 1 tbps

Byte based transfer rates

1000 Bps = 1 Kbps

1000 Kbps = 1 Mbps

1000 Mbps = 1 Gbps

1 Gbps = 1 Tbps

Node, Server, and NIC

Node/Workstation

Node (workstation): A computer becomes a node when it attached to a network. If there are no notes there would be no network.

Server: a computer that facilitates the sharing of data, software, and hardware resources on the network is known as the server. A network can have more than one server. Each server has a unique name by which it is identified by all the nodes on the network.

Server

A server can be of two types:

1. Dedicated Server
2. Non-Dedicated Server

1) Dedicated Server: In Big networks, one computer is reserved for the server's job it helps all nodes to access data, software, and hardware resources. Since it does not double up as a workstation but only manages the network. So, it is known as dedicated server and such types of networks are called Master-Slave networks.

2) Non-Dedicated Server: In small networks, a workstation can double up as a server. These servers are known as Non-Dedicated Servers. Such types of networks are known as peer-to-peer networks.

Network Interface Unit (NIU)

 A Network Interface Unit (NIU) is a device that is attached to each of the nodes and the server which helps to establish communication between the server and node. Without this computers will not be able to perform the operation on network. The NIU basically acts as an interpreter and is also known as Terminal Access Point (TAP) or Network Interface Card (NIC). The manufacturer assign a unique physical address to each NIC and this physical address is known as the MAC address.