Any two notes are required (3.5 marks each). All three are given below; write any two in the exam.

(i) DOM (Document Object Model)

The DOM is a platform- and language-independent programming interface that represents an HTML or XML document as a tree of objects (nodes). The browser builds it when parsing a page, and JavaScript can read and change it, so pages become dynamic.

Node types: document, element, attribute, text, and comment nodes.

document
  └─ html
      ├─ head ─ title
      └─ body
          ├─ h1  ─ "Hello"
          └─ p   ─ "Text"

What JavaScript can do with it:

const h = document.getElementById('title');       // select
h.textContent = 'New heading';                     // change content
h.style.color = 'blue';                            // change style
const p = document.createElement('p');             // create node
p.textContent = 'Added';
document.body.appendChild(p);                      // insert
h.addEventListener('click', () => alert('Hi'));    // handle events

It allows adding, removing, or modifying elements, attributes, and styles, and reacting to events.

(ii) Static vs dynamic web page

Basis	Static page	Dynamic page
Content	Fixed; same for every visitor	Generated at request time; can differ per user
Technology	HTML, CSS (and client-side JS)	Server-side scripting (PHP, Node.js, JSP) with a database
Updates	Manual editing of the file	Content changes through a database or CMS
Interaction	Minimal	Login, forms, search, shopping carts
Development	Simple and quick	More complex
Speed	Faster; can be cached or served from a CDN	Slower due to processing and database calls
Cost / hosting	Cheap	Needs server and database
Examples	Portfolio, brochure page	Facebook, Amazon, online banking

(iii) Fat client vs fat server

Basis	Fat (thick) client	Fat server (thin client)
Processing	Most of the business logic on the client	Most of the logic on the server
Client	Powerful, needs installation	Simple; often just a browser
Server	Mainly stores data	Does processing and stores data
Maintenance	Updates must be installed on every client	Update once on the server
Network use	Lower (after local processing)	Higher, since each action goes to the server
Security	Data and logic exposed on the client	Centralised and easier to secure
Offline use	Possible	Not possible
Examples	Desktop apps, MS Office, games	Traditional web apps, terminal-based systems

Modern single-page applications combine both: a rich JavaScript client with server APIs.