Data representation: Digital systems

Data representation follows the Digital Technologies Knowledge and understanding strand: Years 7–8 AC9TDI8K04 (how and why digital systems represent integers in binary) and AC9TDI8K03 (text, image and audio data as integers). Making data smaller is Years 9–10 (AC9TDI10K03, simple compression). How a web page is made is Years 9–10 (AC9TDI10K02): content, structure and presentation, and why they are kept apart, with no coding needed; the Code pathway's HTML & CSS course puts it to work. No coding needed. The binary cards come from CS Unplugged; doing them with real cards first works well.

Foundations

Data representationBits, binary numbers, and how many patterns a few bits can make.Everything a computer stores is numbers: text as character codes, pictures as pixels, sound as samples. Then how those numbers are stored with only 0s and 1s: binary place value, how many numbers a few bits can hold, logic gates, and the chain from any data down to bytes.

Extensions

Making data smallerSquash data and see what is lost.Compression for Years 9–10: why it matters, run-length encoding (store how many of each colour in turn, and get back exactly the same picture), and lossy compression, which throws away what we won't notice, for good.After: Data representation How a web page is madeWords, tags and style: three layers of every page.For Years 9–10: a web document is three layers, content, structure (HTML) and presentation (CSS). See each layer on its own, change one without touching the others, and find out why keeping them apart matters for whole sites, phones and screen readers. No coding needed; the HTML & CSS course puts it to work.After: Data representation