IGCSE Computer Science Paper 1 Definitions Worksheet: 1.3 Data Storage and Compression (Modules 69–84)
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Key terms
Write what each term means, in your own words.
1
size * 1024
2
1024 per step
3
unit asked
4
pixels = width * height
5
bytes / 1024 / 1024
6
1 kHz = 1000 Hz
7
seconds = minutes x 60
8
size = sample rate x resolution x seconds
9
bits / 8 / 1024
10
file size <= capacity
Answer Key
IGCSE Computer Science Paper 1 · Modules 69–84 · Student wording will vary for definitions
1size * 1024 — To convert to the next smaller unit (GiB to MiB, MiB to KiB, KiB to bytes), multiply by 1024. The answer should be a bigger number than the one you started with.
21024 per step — To convert across several units, divide by 1024 for each step up the ladder or multiply by 1024 for each step down. Bytes to MiB is two steps, so divide by 1024 twice.
3unit asked — Finish a storage calculation by converting the result into the unit the question asks for, then write that unit with your answer, for example 2 MiB.
4pixels = width * height — Total pixels = pixels per row times number of rows. For 1920 x 1080 that is 2,073,600 pixels. This is the first step when working out image file size.
5bytes / 1024 / 1024 — After finding an image size in bytes, divide by 1024 once for KiB, twice for MiB and three times for GiB, to give the answer in the unit the question asks for.
61 kHz = 1000 Hz — Sample rate is measured in hertz (Hz), the number of samples per second. 1 kHz is 1000 Hz, so 44.1 kHz is 44100 Hz. Frequency uses 1000, not 1024.
7seconds = minutes x 60 — Sound length must be in seconds before using it in a file size calculation, so multiply minutes by 60 (add any extra seconds). Length is then the third factor in the formula.
8size = sample rate x resolution x seconds — Uncompressed sound file size in bits is the sample rate (Hz) times the sample resolution (bits) times the length in seconds. Divide the bits by 8 to get bytes.
9bits / 8 / 1024 — Divide the sound size in bits by 8 to get bytes, then by 1024 to get KiB. Divide by 1024 again to get MiB. Stop at the unit the question asks for.
10file size <= capacity — A file fits if its size is less than or equal to the free space. First convert both to the same unit, such as bytes or MiB, then compare the two numbers.