ACARA Digital Technologies Years 7–8 Definitions Worksheet: Representing Text, Images and Sound and Binary Number Representation (Modules 173–188)
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Key terms
Write what each term means, in your own words.
1
Zoom in to samples
2
encoding
3
type -> numbers -> binary
4
two-state system
5
decimal base-10, binary base-2
6
000 001 010 011 100
7
1000 to 1111
8
2^n - 1
9
2^n - 1 >= number
10
powers of 2
Answer Key
ACARA Digital Technologies Years 7–8 · Modules 173–188 · Student wording will vary for definitions
1Zoom in to samples — Zooming far into a waveform in an audio editor like Audacity shows each sample as a dot. A higher project rate gives more dots every second, so the wave is drawn more smoothly.
2encoding — Encoding turns text, images and sound into whole numbers (character codes, RGB pixel values, sound samples), then stores each number as binary 0s and 1s.
3type -> numbers -> binary — Name the data type, say which numbers represent it, then show how they become binary. Give a short example for each, e.g. A is 65 because of ASCII, and 65 is 01000001.
4two-state system — A system with only two possible conditions, like a light switch being off or on. We write the two states as 0 and 1, which is the idea behind binary.
5decimal base-10, binary base-2 — Decimal is base-10 and uses ten digits, 0 to 9. Binary is base-2 and uses only 0 and 1. People use decimal every day, but computers use binary.
6000 001 010 011 100 — Binary counting: when a column is 1 and must go up, it resets to 0 and the next column on the left becomes 1, like carrying from 9 to 10 in decimal.
71000 to 1111 — Binary for 8 to 15. Counting past 7 needs a fourth bit, so 8 is 1000 and the numbers keep a leading 1 up to 1111, which is 15, the largest 4-bit number.
82^n - 1 — The biggest whole number n bits can hold. Counting starts at 0, so n bits give 2^n values and the largest is one less. Example: 4 bits hold 0 to 15 and 8 bits hold 0 to 255.
92^n - 1 >= number — Find the smallest number of bits n whose largest value, 2^n - 1, is at least your number. Example: 20 is too big for 4 bits (max 15), so it needs 5 bits (max 31).
10powers of 2 — Binary place values: 1, 2, 4, 8, 16, 32, 64, 128 and so on. Each place is double the one before it, which is why binary is called base 2.