Web development

Web technology is a general term referring that many languages and multimedia packages that are used with each other to produce dynamic websites. it refers to the the world wide web and focus on the technologies used in creation, maintenance and development of web based applications. web technology involves the use of HTML and CSS. 

6.1 Web Development 

Web development is the building and maintenance of websites; it`s the work that happens behind the scenes to make look great, work fast and perform well with a seamless user experience. web developers do this by using a variety of coding languages. The languages they use depend on the types of tasks they are performing and the platform on which they are working. The field of web development is generally broken down into front-end and back-end. 

Front-end : 

The front-end developers take care of layout, design and interactivity using HTML, CSS and JavaScript. They take an Idea from the drawing board and turn in into reality. what you see and what you use, such as the visual aspect of the website, the drop down menus and the text, are all brought together by the front-end developer, who writes a series of programs to bind and structure the elements, make them look good and add interactivity. These programs are run through a browser. 

Back-end 

Back-end developer engineers what is going on behind the senses. This is where the data is stored and without this data, there would be no frontend. The backend of the web consists of the server that hosts the website, an application for running it and a database to contain the data. The backend developer uses computer programs to ensure that the server, the application and the database run smoothly together. This type of developer needs to analyze what a company`s needs are and provide efficient programming solutions. To do all this amazing stuff they use a variety of server-side languages, like PHP, RUBY, PYTHON and java. 

6.2 Search Engine and Web Browsers 

A search engine is a software system that is designed to carry out web searches (Internet searches), which means to search the World Wide Web in a systematic way for particular information specified in a textual web search query. The search results are generally presented in a line of results, often referred to as search engine results pages (SERPs) The information may be a mix of links to web pages, images, videos, infographics, articles, research papers, and other types of files. Some of the popular search engine are: Google, Bing, Yahoo, Baidu etc. 

Some components of Search Engine: 

Crawler: Crawlers are software programs sometimes referred to the bots. It regularly scans website automatically for URL's, keyword, and links in order to discover the new updates. The crawler can follow the links present on some other webpage. 

Index: Crawlers continuously scans the websites, it develops and index of URLs, links and keywords to make the search results more effective. 

Search Algorithms: The search algorithm is the complete mechanism behind the whole searching process. It is working bu searching for the index and finding for the most suitable web pages by matching keywords that are searched by the users. 

Web browser: 

It is an application software that is developed to retrieve and view the information from the web page or HTML files present on the web servers. The first web browsers is Invented by Sir Tim-Berners-Lee in 1990 and very first graphical web browser was developed in 1993 which is named the mosaic. After that various web browsers were developed. Eg: Google Chrome, Mozilla Firefox, Opera etc. Main Characteristics of web browsers are: 

o It consists Graphical User Interface (GUI) 

o It contains Search Box where user type address and URL 

o Page style can be static and dynamic

o TCP/IP and HTTP protocols are used. 

Difference between search engine and web browsers:

6.3 Internet and web technology

Internet is defined as an information superhighway to access information over the web. It can also defined as:

 It is global system of interconnected computer networks

 It uses standard Internet protocols (TCP/IP)

 Every computer in internet is identified by unique IP address

 IP address is unique set of numbers which identifies a computer location

 DNS is used to give the name to IP address

Advantage

 Internet allows us to communicate with the people sitting at remote locations. There are various apps available on the web that uses intert as a medium of communication. Eg: Facebook, Twitter etc.

 One can surf any kind of information over the internet. Information regarding various topics such as technology, health and science, social studies, GIS .

 Internet also serves a medium entertainment.

 Online banking

 Email

 Downloading the documents and files

 Buy and sell products

 Entertainment

 Job search

 Information

Disadvantage:

 Personal Information: there is always a chance to lose personal information such as name address credit card number.

 Pronography : Also a biggest threat on internt is pornography. There are many pornographic website that can be found, letting your children to use internet which indirectly affects the children healthy mental life.

 Spamming: Spamming corresponds to the unwanted emails in bulk

 Virus: Virus can easily be spread in the internet. Such virus attack may result your system crash or important data may lost.

IP Address: Websites and pages over the internet have a unique worldwide address called IP address eg 192.168.1.1 but a domain name eg facebook,com is used to refer to a website as it is easy to remember. There are two versions of IP specification in use now: IPv4 and IPv6. IPv4 is most widely used version currently. An IPv4 address contains 4 contains and each part will be a number between 0 and 255. Eg: 192.168.1.6. An IPv6 address has 8 part and each part must be a hexadecimal number between 0 and FFFF eg: FF3:9B3D:999:0:FF12:420:20:444D Domain Name System (DNS):

Domain Name System provides a mapping domain name like www.psc.gov.np and IP address like 192.168.1.3. When we type a domain name www.psc.gov.np in the browser it will use DBS to resolve and find the IP address and browsers then uses the IP address to connect to the correct machine. Web application: Web application is an application software that runs on server and we can access using a web browser client. For instance consider this website you access it using a client browser but it is deployed on a server located elsewhere. eg: PHP, ASP, Servlets, these are the server side technologies. Web server:

Web server is a software that helps to deliver web content to the client through internet using HTTP protocol. Some of the commonly used web servers are Apache web server, Microsoft Internet Information Services and Google web server etc.

Web browser: Web browser can read HTML documents and compose them into visible or audible web pages. JSP (Java server page) based on Java and ASP( Active server page) based on .net or open source PHP pages all finally generate HTML page with other client side technologies like JavaScript and CSS. Cookies: A Cookies is a small piece of data sent from website and stored in a user’s web browser while user is browsing that website. A cookie is also known as HTTP cookie, web cookie or browser cookie. A website usually use cookie to store preference information session identification data or insensitive user information. The user is free to modify them or delete them and usually cleared when the browser cache is cleared. URI(Uniform resource identifier): URI(Uniform resource identifier) is a string characters used to identify name of the resource. Such identification enables interation with representation of the resource over a network, typically the WWW using specific protocols.

URL(Uniform resource locator): which is most common and is frequently referred to informally as a web address. Eg: www.facebook.com URN(Uniform resource name): which is rarely seen and was designed to complement URLs by providing a mechanism for the identification of resources in particular namespace.