Web Development: History and Evolution

• Understanding web development is crucial in IT and computer science
• Web development involves creating and maintaining websites with user-friendly, visually appealing, and functional platforms
• Web development facilitates digital content delivery, communication, business, and innovation

History of Web Development

• Tim Berners-Lee invented the World Wide Web (WWW) in 1989 at CERN
• Berners-Lee's vision was a global platform for easy information sharing
• The web was initially designed for scientists to collaborate via hypertext documents
• Berners-Lee developed key components like the first web browser, server, and HTML
• HTML (HyperText Markup Language) is the foundational markup language for structuring web page information

Evolution of Websites

• Early websites (1990s) were static, consisting of plain text and basic images
• Content was hardcoded in HTML, displayed the same way to every visitor
• These websites lacked interactivity and required manual content updates
• Dynamic websites (late 1990s - early 2000s) introduced personalized and interactive content
• Server-side scripting (e.g., PHP, ASP) and databases (e.g., MySQL) enabled dynamic content generation
• This evolution enabled features like login systems, e-commerce, and CMS
• Modern web platforms are highly interactive and feature-rich
• Frameworks like React, Angular, and Vue.js enhance front-end experiences
• Back-end tools like Node.js and Django handle server-side operations
• Cloud technologies, APIs, and microservices enable faster and more scalable content delivery
• Modern websites include real-time interactions, mobile responsiveness, and progressive web apps (PWAs)

Client-Server Architecture

• Client-server architecture is the fundamental design model for web systems
• Clients and servers are the two main entities that interact to fulfill user requests and deliver responses
• The client is any device or application that initiates requests for resources or services
• Web browsers, mobile apps, and desktop software are examples of clients
• The server is a system or application that processes client requests
• Servers retrieve requested resources (e.g., data, files, web pages) and send results back to the client
• A web browser sends a request to a web server for a webpage
• A mobile banking app communicates with an application server to retrieve account information
• Clients include devices like PCs, laptops, tablets, smartphones, or browsers
• Clients send requests using protocols like HTTP/HTTPS and display server responses
• Client requests are examples such as loading a webpage, submitting a form, or retrieving an image
• Servers are backend systems like web servers, application servers, or database servers
• Servers receive, process, and respond to client requests
• Servers retrieve data from databases, perform computations, or generate dynamic web pages

Request-Response Cycle

• The client sends a request to the server for a specific resource using a URL (Uniform Resource Locator)
• The server processes the request, retrieves necessary resources, and prepares a response
• The server sends the processed data back to the client
• The client processes and renders the received data for display

HTTP/HTTPS Protocols

• HTTP (HyperText Transfer Protocol) is the standard protocol for transmitting requests and responses
• HTTPS (HTTP Secure) is an encrypted version of HTTP that ensures secure communication

Types of Servers

• Web Servers handle HTTP/HTTPS requests and deliver static or dynamic content to clients and examples include Apache, Nginx
• Application Servers perform complex tasks like running business logic and examples include Node.js, Django, Flask
• Database Servers store, retrieve, and manage data for web applications and some examples include MySQL, PostgreSQL, MongoDB

Browser Interaction Examples

• A user types "www.example.com" into a web browser and presses Enter
• The browser queries a DNS server to resolve "www.example.com" into an IP address
• The browser sends an HTTP GET request to the resolved IP address (web server)
• The web server processes the request and sends the necessary files back to the browser
• The browser renders the webpage and displays it to the user
• Client browsers include sending a request
• Web servers include receiving the request, processing it, and interacting with the database
• Database Servers involves, responding to queries made by the web server
• Web Server Response is sending the requested content (HTML, CSS, JavaScript) back to the client

Basics of HTML, CSS, and JavaScript

• Web development relies on HTML, CSS, and JavaScript
• Each technology has a distinct role in creating modern, functional, and visually appealing web pages

HTML (Structure)

• HTML (HyperText Markup Language) provides the skeleton or structure of a webpage
• It defines the arrangement and content of elements on the page
• HTML specifies the elements of a webpage, such as headings, paragraphs, links, images, and forms

Key HTML Elements

• <html> is the root element that wraps the entire content of the webpage
• <head> contains meta information like the page title and links to external files
• <body> holds the visible content displayed on the webpage

Common HTML Elements

• Headings: <h1> to <h6> for titles and subtitles
• Paragraphs: <p> to structure text into blocks
• Links: <a href="url">Text</a> to navigate between pages or websites
• Images: <img src="image_url" alt="description"> to embed visuals

CSS (Styling)

• CSS (Cascading Style Sheets) enhances the visual appearance of a webpage
• It controls colors, fonts, layouts, and other design aspects
• CSS applies styles to HTML elements to improve aesthetics and usability

CSS Syntax

• Selectors: Target specific HTML elements (e.g., h1, .class, #id)
• Properties: Define what to style (e.g., color, font-size)
• Values: Specify the style details (e.g., red, 16px)

CSS Examples

• Text styling, background styling, and layout styling are some uses
• Setting h1 font style with size and color is an example of text styling
• Setting the background color: example body {background-color: #f0f0f0;}
• Setting display with flex, justify content and align items are layout style

JavaScript (Interactivity)

• JavaScript adds dynamic functionality and makes a webpage interactive
• It responds to user actions like clicks, hovers, and key presses
• It controls the behavior of elements on a webpage, enabling features like forms, animations, and dynamic content updates

JavaScript Syntax

• Variables: Store data
• Functions: Perform tasks
• Events: Respond to user actions