Angel Barbie

NETWORKS

Networking refers to group of autonomous individual computers interconnected to each other for sharing resources. Data, information, software and even hardware can be shared through networks which are either wired or wireless.

Advantages of Networking –

Ø Speed is high;

Ø Cost is low;

Ø Security is strong;

Ø Centralised software management;

Ø Resource sharing;

Ø Electronic mail(E-mail);

Ø Flexible access;

Ø Workgroup Computing.

Application of Networking –

1. Communication;

2. Sharing resources;

3. Sharing software;

4. Data sharing.

COMMUNICATION MODEL ON A NETWORK

Data communication is called local communication, if the communicating devices are in the same building or a restricted geographical area. The device that transmits the data is called source and the device that receives the transmitted data is called receiver. The data moves from a sender to a receiver, through a medium (wired or wireless) and forms the Transmission System.

COMPONENTS OF A NETWORK –

1) Message – The information or data to be communicated;

2) Sender – The device that generates and sends the message;

3) Receiver- The device that receives the message;

4) Medium – The channel or a medium through which the message is carried from the sender to receiver;

5) Protocol – A set of rules that govern the communication between the devices.

TYPES OF NETWORKS –

Depending upon the geographical area that the networks can cover, they are classified as below:

1. Local Area Network (LAN) – Within a small area, i.e., a room or a building, e.g., a school or an office network;

2. Metropolitan Area Network (MAN) – Spanning a city or multiple campuses, e.g. cable TV network;

3. Wide Area Network (WAN) – Coverage over a large area like a country, continent or the world, e.g. The Internet;

4. Personal Area Network (PAN) – Used for personal needs and can network within a small space through computers, phones and other personal devices. The transfers are done on a wireless network, called WPAN (Wireless Personal Area Network), e.g. Bluetooth Personal Area Network;

5. Campus Area Network (CAN) – Network of interconnected Local Area Network (LAN) in restricted Area. It is also called Corporate Area Network.

NETWORK TERMINOLOGIES -

Ø Internet is a private network within an enterprise;

Ø URL (Uniform Resource Locator) is also known as a web address, e.g.:- http://google.com

Ø ISP (Internet Service Provider) is the company that provides the internet connection and services to Internet. E.g. Airtel, Jio, Vodafone etc.;

Ø IP (Internet Protocol Address) or IP Address, is a numerical address that identifies your computer on a network;

Ø Domain or DNS – A domain name is the website’s name. Internet uses can access the website using its domain name. It can be any combination of letters and numbers and it has domain name extensions such as ‘.com’, ‘.net’, ‘.in’, ‘.org’ etc. For example, www.wikipedia.org.

Ø A Domain Name System Server (DNS server) contains a database of domain names and the corresponding IP addresses. Every Internet user has used a DNS without realising it. Its job is to convert a domain name into an IP address like 192.13.74.6. For example, if someone uses GoDaddy’s DNS settings, users will reach GoDaddy’s servers when using that website stored in that server.

Ø Web Portal – A web portal is customised website that contains information from lot of sources in a consistent and informed manner. E.g. Government portals, Company portals etc.

Ø Modem – A modem is a hardware device that allows a computer to send and receive

data over a telephone line or a cable or satellite connection. The modem converts data between analog and digital formats in real time for two -way network communication. It is named as Modem as a combination of two words Modulator and DE-Modulator. Modulator as it connects digital to analog and De-modulator as it connects analog to digital.

Ø Router – A router is a device that passes network traffic (data on the internet) from our local devices to the Internet and vice versa.

Ø Hub – For connecting several computers within a network a hub is used. A hub

contains several posts (6,8,16 or 24) where networking devices can be attached. The more the number of parts, more number of computers or networking devices attached to it.

Ø Switch – A switch is like a hub, but works in a slightly different way than hub. A hub

simply replicates the data it receives from one port to all other ports (called broadcasting). The destination computer receives the data, but the other computers reject it. The switch on the other hand receives a data from a port which it is tended by looking at the MAC(Media Access Control) address of that machine.

Ø Gateway – A gateway is a device that routes traffic between different types of networks and protocols. E.g. Router.

Ø Bridge – A bridge is a device used to join and route traffic on two similar types of networks. E.g., A bridge can join two separate hubs.

Ø Link – The link is the physical and logical network component used to interconnect hosts on nodes in the network and a link protocol is a suite of methods and standards that operate only between adjacent network nodes of a local area network segment or a wide area network connection.

Ø Bandwidth – Bandwidth refers to the available or consumed data capacity and sometimes data transfer rate. The amount of data that can be transmitted from one point to another in a second. Network bandwidth is usually expressed in bits per second (bps).

Ø Website – A Website is a collection of related pages, with a domain name. It is published on a web server to be available for users all over the world.

Webpage is a document with hyperlinks and hypertexts. Many webpages contribute to make website.

Ø Hyperlink - A text or graphic in a document or a webpage that links to another page. It allows the user to travel from page to page in a website.

Hypertext is the text which contains links to other texts.

PROTOCOLS

There are a set of rules or standards that define the method of communicating the data on a network. Some of them are:

Ø HTTP (Hypertext Transfer Protocol)

Ø HTTPS (Hypertext Transfer Protocol – Securely)

Ø FTP (File Transfer Protocol)

Transmission Control Protocol/Internet Protocol (TCP/IP) –

IP standard tells packets (pieces of information which are getting transmitted) where to go and how to get there. The TCP is responsible for ensuring that the data is transmitted reliably on the Internet. It checks the packets and submits requests for re-transmissions if any error is found. Some of the TCPs are:

1. IMAP (Internet Message Access Protocol)

2. POP (Post Office Protocol)

3. SMTP (Simple Mail Transfer Protocol)

CLOUD COMPUTING

Cloud computing refers to portable storage accessible through a Network (generally Internet). They provide storage space to users to store data and allows to access it from any part of the world at any time. Google plus and Drop box are some famous examples of cloud computing applications.

Storing and Sharing Data over Cloud –

Saving the data to a remote storage system which is maintained by a third party which provides this service is called the cloud/hosting provider. The Internet provides the connection between your computer and the database and you don’t need to carry a physical storage device with you or use the same computer to save and read your information. The facilities that house cloud storage system are called data centres.

For example, Web e-mail providers like ‘Gmail’, ‘Hotmail’, and ‘Yahoo! Mail’, store e-mail messages on their own servers. These mails can be accessed from anywhere in the world at any time, by the e-mail address the message is sent to.

Types of Clouds

1. Public Cloud

2. Private Cloud

3. Community Cloud

4. Hybrid Cloud (a mixture of public and private cloud)

Service Models of Cloud Computing –

Cloud computing is based on three service models :

1. Infrastructure – as- a – Service (IAAS) – e.g. Amazon Web Service (AWS)

2. Protocol – as - a- Service (PAAS) –e.g. Developers can creat specific applications for the Facebook platform using proprietary APIs and make that app available to any Facebook user.

Software – as – a – Service (SAAS) – e.g. Google Docs, Drop Box etc.

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PROGRAMME CODING- JAVA

Programming is the process of translating the algorithm and flowchart to a source code in

the syntax of a programming language, so that, it can be executed by the computer and a useful output can be obtained. Without an algorithm (steps to do a task) there can be no programme.

A programme is a set of instructions that instructs the computer to perform a task and results in an output. To get an expected output, instructions need to follow the rules of the programming language, which the programmer is using. These rules are called syntax.

A programmer, writes the programme in high level language. A high level language is any programming language that enables development of a programme in a much more user friendly programming context. It is independent of the computer’s hardware architecture. It focuses more, on the programming logic rather than the underlying hardware components such as memory addressing and register utilisation.

The translation of the programme from high level to low level language is done by Compilers and Interpreters, which themselves are the programmes written in low level languages.

BASIC, C / C++ and Java are popular examples of high level languages.

The interpreter reads a programme line and converts each line to machine language and executes it.

A compiler on the other hand, translates all the instructions of high level source code written by a programmer in a high level programming language into low level language (binary codes) in machine language.

ERRORS OF A PROGRAMME –

1. Syntax Errors - When the grammatical rules of a programming language are violated, an error that occurs is called a syntax error. For example, in Java, every statement must end with a “;”. If this “;” is omitted, it will be considered as a syntax error.

2. Run Time Errors - The errors that occur during the execution (while the programme is being run) of a programme are called Run Time errors. For example, if there is an instruction, which attempts to divide an integer by a zero, it results in a Run Time error “Division by zero” message.

3. Logical Errors –When there is no syntax or run time error, the programme executes, but provides an unexpected output which could be due to an incorrect logic, the programme is said to have logical error. For example, a programme which should convert a temperature in Celsius to Fahrenheit gives an incorrect answer, could have suffered a logical error due to wrong formula.

TOKENS OF A PROGRAMMING LANGUAGE –

Tokens are the smallest building block of a programme. They are the fundamental units, using which a programme is built. Some of the tokens in a programming language are :

(i) Keywords – int, float, char, etc.

(ii) Identifiers - Names given to different parts of a programmes. They are named by programmers while following certain rules :

(a) Starts with an alphabet or underscore.

(b) First character must be followed by alphabets, digits or underscore.

(c) Space and special characters are nor allowed.

(d) Keywords cannot be the names of the identifiers.

(iii) Literals(Variables) – They are constant values. The different tupes of literals are:

(a) Integer literals, e.g. 90,

(b) Decimal literals, e.g. 89.23 or 89.23f,

(c) Character literals, e.g. ‘a’,

(d) Boolean literals, e.g. true and false,

(e)String literals, e.g. “aditi”.

iv) Punctuator – They are also called separators. For example, comma (,) and semicolon (;).

(v) Operators – Symbols applied on operands and yield a specific result.

TYPES OF OPERATORS –

1. Assignment Operators –

Equal to sign (=) is an assignment operator which is used to assign a value to a variable. Variable stores a value based on the data type of the variable. E.G., int x=10;

Here, variable x is declared as an integer variable. It can store an integer number (i.e., 10)

2. Arithmatic Operators –

3. Relational Operators –

4. Logical Operator –

Variables –

A variable is a memory location that stores data/value. The type of data that it stores depends on the data type used to declare a variable. The value of the variable can change in a program. Variables are named by programmers following the rules for naming identifiers.

Data Types –

A data type represents a keyword of the programming language that allocates sufficient storage space (memory for the data)

A program is given below to compute the area of a rectangle with length =50 cm and breadth = 15 cm. The following is to be written in the “BlueJ” application which uses the programming language of Java.

// compute the area of a rectangle//

class prg

{

void display()

{

int length =50, breadth = 15;

int area = length * breadth;

System.out.println (“Area of given rectangle =”+area);

}//end of method

}//end of class

To see the output of the program, follow the given steps :

1. After typing the program,click on ‘compile’.

2. Close the window and right click on the file named prg;

3. Choose ‘create object’ and a window will open up naming the program as prg 1.Click on OK.

4. A red box will appear at the bottom of the window. Click and open it.

5. The output of the program will be shown as :

“Area of given rectangle =750”

Decision making statement –

The decision making statements form the selection construct of the program. The statements of the program are executed based on whether the condition is true or false. The flow of control is selected based on the result of the condition. E.g., if – else, if – else – if, switch.

General syntax of if – else :

if (text expression)

{

// Block containing any valid Java statements if the text expression is evaluated to true.//

}

else

{

// Block containing any valid Java statements if the text expression is evaluated to false.//

}

Given below is a program following the above syntax:

// to input a number and check whether it is positive or negative.//

class prgm

{

void display (int n)

{ if (n>0)

{

System –out.println (n+”is a negative number”);

}

else if (n<0)

{

System.out.println(n + “is a negative number”);

}

else

{

System.out.println(n + “ is a zero”);

}

}//end of display

}//end of class

The way to view the output will remain the same except for a slight change, i.e. once the red box with the name of the class appears at the bottom of the window,we will have to:

(i) Right click on it and choose ‘ void display ()”.

(ii) A box will open where we can input any numerical for the variable. This is to be done at times when the value of the variable is not mentioned in the code itself.

(iii) Once the value has been inserted, click on OK and click on the red box to view the output.

E.g.> In the above program (prgm) if n=5, then the output will be shown as “5 is a positive number.”

Angel Barbie

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