Grade 9 · Unit 1: Data representation · IGCSE Computer Science

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Revision videos, vocabulary practice and written questions for IGCSE.

IGCSE Computer Science

9 videos

Revision videos for IGCSE Computer Science, unit by unit: Grade 9 data representation, data transmission and hardware.

Grade 9 · Unit 1: Data representation

2:41

Denary, binary and hexadecimal

Place values, converting denary to binary and back, and why hex is used for bytes.

binaryhexadecimaldenary
2:30

Binary addition, overflow and shifts

Adding binary numbers with carries, overflow when a ninth bit is needed, and logical shifts as multiply and divide.

binary additionoverflowlogical shift
2:12

Two's complement

Negative numbers in binary: the -128 place value, invert and add one, and reading a signed byte.

two's complementnegative numbers
1:45

Text: ASCII and Unicode

Character sets give every character a code. ASCII's 128 codes, Unicode's millions, and the storage trade-off.

ASCIIUnicodecharacter set
1:27

Images

Pixels, resolution, colour depth, image file size and metadata.

pixelsresolutioncolour depth
1:38

Sound

Sampling an analogue wave: sample rate, bit depth, quality against file size.

samplingsample ratebit depth
1:50

Storage units and file sizes

Bit to pebibyte in steps of 1024, and calculating image and sound file sizes.

KiBMiBfile size
1:58

Compression

Why files are compressed, lossy against lossless, and run-length encoding step by step.

lossylosslessRLE
5:38

Unit 1 quiz

Ten questions with a think-time countdown and explained answers.

quizrevision