Understanding Computer Networks

Networks and Their Types

• A network is a system of interconnected computers and devices that share data and resources.
• LAN (Local Area Network) covers small areas such as homes, offices, or schools, e.g., a university lab connected via Ethernet.
• WAN (Wide Area Network) covers large geographical areas such as cities or countries; the Internet is the largest WAN.
• MAN (Metropolitan Area Network) covers a city or large campus, like a city-wide Wi-Fi network.
• PAN (Personal Area Network) is a small network for personal devices, e.g., Bluetooth connection between a smartphone and wireless earbuds.

Networking Technologies

• Ethernet is a wired technology used for local networks.
• Wi-Fi is a wireless technology used for Internet access.
• 5G is a high-speed mobile internet for modern smartphones.
• Fiber Optics provides high-speed internet via light signals.

New Trends in Networking

• Cloud Computing involves storing and accessing data over the internet instead of local devices.
• Edge Computing refers to processing data near the source instead of sending it to a central cloud.
• IoT (Internet of Things) includes smart devices like home assistants like Alexa and Google Home.

The Internet

• The Internet is a network of computers communicating using standard protocols.
• In the 1960s, the U.S. military developed ARPANET which was a precursor to the internet.
• TCP/IP was established as the internet’s communication standard in 1983.
• Tim Berners-Lee invented the World Wide Web in 1990.
• From 2000s-Present the evolution of broadband, social media, and mobile internet has occurred.

How the Internet Works

• A user enters a URL in a browser.
• The browser requests the page from a web server.
• The server sends HTML, CSS, and JavaScript files to the browser.
• The browser processes these files and displays the web page.

The Web (World Wide Web)

• The Web is an information system that allows users to access documents via web browsers.
• Tim Berners-Lee invented the web in 1989.
• The first website (info.cern.ch) was created in 1991.
• Social media, web applications, and cloud computing surged in the 2000s.

Web Usage

• Google Search (www.google.com) allows users to search for information.
• YouTube (www.youtube.com) provides video streaming.

Internet Protocols

• TCP/IP (Transmission Control Protocol/Internet Protocol) ensures data packets are correctly sent and received, and is used when loading a web page without missing parts.
• HTTP (Hypertext Transfer Protocol) transfers web pages from servers to browsers, as demonstrated when clicking a link to load a new page.
• HTTPS (Secure HTTP) encrypts web traffic for security as seen on online banking websites.
• FTP (File Transfer Protocol) transfers files between computers.
• DNS (Domain Name System) converts domain names (e.g., www.example.com) into IP addresses (e.g., 192.168.1.1).

Web Domains and Related Concepts

• A domain name is a user-friendly web address that points to a server, such as www.facebook.com.
• A name server is a database that translates domain names into IP addresses.
• WWW (World Wide Web) is a collection of linked documents and multimedia accessed via web browsers.
• A web browser is a software application for browsing the web, e.g., Google Chrome, Mozilla Firefox, Microsoft Edge.
• A web server is a computer that stores and serves web pages and examples include Apache, Nginx, Microsoft IIS.

Web Development Technologies

• HTML (Hypertext Markup Language) is the standard language for creating web pages.
• XHTML (Extensible HTML) is a stricter version of HTML, following XML syntax.
• CSS (Cascading Style Sheets) is used for styling web pages by setting layout, color, fonts, and responsiveness.
• JavaScript (JS) is a programming language for adding interactivity to web pages.

Web Programming Trends

• Progressive Web Apps (PWA) work on both web and mobile platforms.
• AI and Machine Learning can be found in chatbots and recommendation systems on the web.
• Serverless Architecture involves running code without managing servers.
• Blockchain & Web3 entail decentralized web applications.

Fundamental Web Technologies

• Hypertext Transfer Protocol (HTTP) is a protocol for transferring data between clients (browsers) and servers, supporting methods like GET, POST, and DELETE; modern versions like HTTP/2 and HTTP/3 offer faster data transfer.
• Uniform Resource Locator (URL) is a structured address system for locating web resources.
• Domain Name System (DNS) translates human-readable domain names into IP addresses used by machines.
• Web Servers are software such as Apache, NGINX, and Microsoft IIS that host web content and respond to client requests.
• Web Browsers are client software that interprets and renders web content for users.

Concepts of Web Programming

• Web programming includes client-side and server-side components.
• Client-Side Programming runs on users' browsers, focusing on creating responsive and interactive user interfaces, using HTML, CSS, and JavaScript.
• Client-side programming reduces server load by handling local processing and enhances user experience via dynamic updates using AJAX
• Server-Side Programming executes programs on the server, handling database interactions, user authentication, and business logic for dynamic web applications.

Why Use Server-Side Scripting

• Server-side scripting secures data processing, supports database interactions, enables dynamic content generation, and enhances website scalability.
• It executes on the server, focusing on backend logic, database management, and dynamic content with languages like PHP, Node.js, Python, Ruby on Rails, and Java.
• Server-side scripting handles complex business logic and provides data security/validation before sending information to the client.
• Client and server communicate through APIs and protocols like REST or GraphQL.

HTML and CSS

• HTML (Hypertext Markup Language) provides the structure and content of web pages.
• HTML is composed of elements (tags) for headings, paragraphs, and images, improving accessibility and SEO with semantic tags and supports multimedia with video and audio tags.
• CSS (Cascading Style Sheets) controls the presentation and styling of HTML content, offering layout, color, fonts, and responsiveness and supports selectors, classes, and ID-based styling.
• Advanced CSS tools such as CSS Grid and Flexbox, simplify responsive and adaptive layouts and Media Queries enable responsive design for various screen sizes.
• CSS Preprocessors like SASS and LESS extend CSS capabilities with variables, nesting, and mixins.

JavaScript

• JavaScript is a lightweight, interpreted language that produces interactive web content and executes directly in browsers via JavaScript engines.
• Key features of JS include, DOM Manipulation which enables real-time updates, Event Handling captures user interactions, and Asynchronous Programming handles background tasks using Promises, async/await, and AJAX.
• APIs are used for accessing browser features like Geolocation, LocalStorage, and Canvas and Libraries/Frameworks such as jQuery, ReactJS, and VueJS, which enhance productivity and simplify complex tasks.

Server-Side Scripting

• Server-side scripting executes on the server rather than in the user's browser.
• The processes done on the server-side include processing form data, interacting with databases, handling authentication, and generating dynamic web pages.

.NET for Server-Side Scripting

• .NET is a software development framework by Microsoft that supports languages like C# and VB.NET and provides environment for building web applications.
• ASP.NET is a server-side framework for creating web applications, APIs, and dynamic websites: supports C# and VB.NET, works with MVC architecture, and provides built-in authentication, authorization, web APIs and microservices as well as Razor Pages.

ASP.NET Web Development Models

• Web Forms (Old Approach) uses drag-and-drop controls and an event-driven model, similar to Windows Forms.
• ASP.NET MVC separates logic, UI, and data, following the MVC pattern of Model, View, Controller.

Modern .NET Trends

• Blazor builds interactive WebAssembly applications using C#.
• Minimal APIs are lightweight APIs for fast web development.
• Cloud Integration involves deploying .NET apps using Azure, AWS, or Google Cloud.
• Microservices Architecture builds scalable services using Docker and Kubernetes.

Fundamentals of PHP

• PHP (Hypertext Preprocessor) is an open-source, server-side scripting language used for web development and is fast, efficient, and compatible with various databases.
• PHP is open-source, free, platform-independent, supports databases like MySQL and MongoDB and is compatible with HTML, JavaScript, and CSS.

Procedural PHP

• Procedural PHP has simple structure, and is suitable for small projects.

Object-Oriented PHP

• Object-Oriented PHP is more organized, scalable, and suitable for large apps.

PHP Frameworks

• PHP Frameworks such as Laravel and Symfony are used or structured development and enhances security along with scalability.

Modern PHP Trends

• Laravel Framework happens to be the most popular PHP framework.
• Headless CMS with PHP uses PHP for backend with React frontend.
• Cloud-Based PHP Apps deploy PHP applications on AWS, Azure, and DigitalOcean.
• Microservices with PHP build scalable applications using microservices architecture.

Python (Django)

• Django is a Python web framework that encourages rapid pragmatic design.
• Django provides built-in tools for authentication and admin panels, protection against SQL injection, XSS, CSRF and clickjacking along with being scalable.

Node.js (Express.js)

• Node.js is an open-source, cross-platform runtime built on Chrome's V8 JavaScript engine. Developers can use JavaScript for backend development.
• Node.js is asynchronous, non-blocking, uses Google's V8 engine, supports JavaScript for both frontend and backend, and uses an event-driven architecture.