Web Development and Multimedia Applications
Client side and server side
HTML structures content, CSS controls presentation and JavaScript adds behaviour in the browser. Server-side languages such as PHP, Python, Java and Node.js generate pages, query databases and enforce business logic. HTTP is stateless, so cookies, sessions and hidden fields carry state between requests. GET places data in the URL, is length-limited and cacheable; POST places data in the body. Status codes include 200 OK, 301 moved, 404 not found and 500 server error.
Site design and hosting
A URL has the form protocol://host:port/path?query#fragment. Responsive design uses fluid grids, flexible images and media queries. Accessibility, consistent navigation and sitemaps matter. Hosting options are shared, VPS, dedicated and cloud; domains need DNS records such as A, CNAME and MX.
Multimedia
Bitmap graphics are grids of pixels with fixed resolution and larger files; vector graphics use mathematical paths and scale without loss. Key concepts are resolution in ppi or dpi, colour depth in bits per pixel, and sampling rate and bit depth for audio. Formats include JPEG (lossy, photographs), PNG (lossless, transparency), GIF (256 colours, animation), SVG (vector), MP3/AAC and MP4. Compression is lossy or lossless.
Trap: file-size calculations fail when bits and bytes are confused, and JPEG is unsuitable for line art or transparency.
Worked example: an uncompressed 800 × 600 image at 24-bit colour takes 800 × 600 × 24 = 11,520,000 bits; divide by 8 for 1,440,000 bytes, or about 1.4 MB. Rule of thumb: pixels × bits per pixel ÷ 8 = bytes. Adding audio or video length × bitrate ÷ 8 gives the same style of answer.