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Web Technology Dr. M. Durairaj, Ph.D.
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Web Technology Web technology refers to the means by which computers communicate with each other using markup languages and multimedia packages. It gives us a way to interact with hosted information, like websites. Web technology involves the use of hypertext markup language (HTML) and cascading style sheets (CSS).
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History of Internet and World Wide Web
Introduction More than two billion Internet users 30% of the earth’s population Billion general-purpose computers Billions or more embedded computers, cell phones, smartphones, home appliances and automobiles and more. We learn the technology which is portable.
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Client-side programming technologies
HyperText Markup Language 5 (HTML5) Cascading Style Sheets (CSS3) Powerful, dynamic, fun features, audio, video, animation, drawings and effects…. Java Script – the language for client side jQuery – the JavaScript Library Ajax (Asynchronous JavaScript And XML) development, better performing, usable applications.
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Servier-Side programming
The applications that respond to requests from client-side Searching, browsing, checking bank-account, ordering in amazon, bidding in eBay, ordering tickets, etc. PHP, ASP.NET (both C# and VB), JavaServer Faces Moore’s Law – (Inter Chief Gorden Moore) Every year cost of product escalates, but computer h/w cost reduces.
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The Internet in Industry and Research
Technology companies, such as Apple, IBM, etc. recruits more peoples. Most computer applications run which are not connected to other computers. Internet applications used in research & industry. E.g. Electronic health records, Human Genome Project AMBER Alert – America’s Missing: Broadcast Emergency Response World Community Grid – people can donate their unused computers One Laptop Per Child – provides low power inexpensive labtops. Cloud Computing – Amazon S3, EC2, Azure, etc. GPS – Global Positioning System, Robots – NASA’s Mars rover, military combat, deep sea and space exploration. , Instant Messaging, Video chat and FTP
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HTML5, CSS3, JavaScript, Canvas and jQuery
Client side web applications HTML5 – markup languages for content and structure of web pages. Extraordinary range of devices: Smartphones, tablet computers, notebooks, desktops, special purpose devices Creating table, headers, navigation areas, footers, sections, figures, captions, etc. XHTML (Extensible Hyper Text Markup Language) based on XML (eXtensible Markup Language) CSS – Cascading Style Sheets Provides capabilities to control document’s presentation – font, spaces, sizes, color, positioning, etc)
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JavaScript Build dynamic web pages ( can be modified on the fly) Created by Netscape Standardized by ECMA (European Computer Manufacturers Association) jQuery Popular of hundred of JavaScripts libraries
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Evolution of the Internet and WWW
Late 1960s – ARPA (the Advanced Research Project Agency) Networking of computers has bps At that time 110 bps through telephone Eventually ARPANET – evolved into today’s internet. Packet Switching Primary goal of ARPANET was to allow multiple user to send and receive simultaneously Packet contains address, error-control and sequencing information TCP/IP (Transmission Control Protocol / Internet Protocol) by ARPA IP – truly a network of networks, current versions Ipv4 and next generation IPv6.
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World Wide Web, HTML, HTTP
Explosive Growth World Wide Web, HTML, HTTP 1989, Tim Berners-Lee of CERN (European Organization for Nuclear Research) developed a technology for sharing info. via hyperlinked HTTP – he wrote protocol – communications protocol used to send information over the web. HTTPS – secure the information Mosaic, Netscape, Emergence of Web 2.0 1993 – Mosaic browser – user friendly graphical interface Google’s Web 2.0 – YouTube (video sharing), Facebook (social networking), Twitter (microblogging), Groupon (social commerce), Foursquare (mobile check-in), Skype (Internet telephony), Wikipedia (online encyclopedia)
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Web Basics Web page – HTML Hyperlinks
URIs (Uniform Resource Identifiers) and URLs (Uniform Resource Locators) Web Servers – make available of resources. Apache’s HTTP server, MS IIS DNS – Domain Name System- maintains the hostnames and corresponding IP addresses
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Making a Request and Receiving a Response
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HTTP Headers Provides additional information about the data that will be sent. Content-type: text/html MIME – Multipurpose Internet Mail Extensions Type of content that server sends HTTP get and post Requests Two request methods, get and post Client-Side Caching (save on disk)
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Data Hierarchy Data hierarchy becomes larges and more complex
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Levels of the data hierarchy
Bits – smallest data item – value 0 and 1 Characters – decimal (0-9), letters, Special symbols Fields – composed of bits – characters, bytes Records- several related fields Files – group of related records
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Operating Systems OS are s/w that make using computes more convenient for users, developers, admins Allows concurrent Windows 10, Mac OS, Unix, Linux, Sun OS, Android, IOS, etc. Desktop and Notebook OS: Mobile OS – iOS for iPhone, iPad and iPod for Touch, Android Types of Programming Languages Instructions which computers understand High level – Machine level (conversion by translators) C, C++, Object-C, Visual Basic, Visual C#, Java, etc. PHP, Python, JavaScript, Ruby on Rails, Scala
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Object Technology Aim: Building s/w quickly, correctly and economically. Objects – more precisely the class – comes from a reusable s/w components. Attributes (name, color, size) Behaviors (calculating, moving, communicating) Object E.g. Automobile as an Object Methods and Classes – bank deposit, withdraw, inquire (a method) Instantiation Build a car before driving Reuse Can be reused many times to build many cars
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Messages and Method Calls Attributes and Instance Variables
Car pedal sends message to cars Attributes and Instance Variables Car has attributes (color, no in door), Every car maintains its own attributes Encapsulation Classes encapsulate (wrap) attributes and methods into objects – information hiding Inheritance New class of objects can be created quickly and conveniently by inheritance New class observes characteristics from existing class
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End of Unit – I Thank you
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