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SingaporeComputer Science

Data Representation

5 dot points across 5 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do we add binary numbers by hand, and what happens when the result is too big for the register?

Perform binary addition showing carries, and explain overflow when a result exceeds the fixed width of a register
A focused answer to the O-Level Computing point on binary addition. Adding binary numbers column by column with carries, checking the result against denary, and understanding overflow in a fixed-width register.
6 min answer →

How do we convert reliably between denary, binary and hexadecimal by hand?

Convert whole numbers between denary, binary and hexadecimal using place value, repeated division and nibble grouping
A focused answer to the O-Level Computing point on number base conversion. Converting between denary, binary and hexadecimal using place value, repeated division by two, and grouping binary into nibbles.
7 min answer →

How do we measure amounts of data, and how does compression make files smaller?

Use units of storage from bit to terabyte, and explain lossless and lossy compression and why files are compressed
A focused answer to the O-Level Computing point on data measurement. Units from bit and byte up to terabyte, calculating file sizes, and the difference between lossless and lossy compression and why files are compressed.
6 min answer →

Why do computers use binary, and how do place value and hexadecimal help us read those binary patterns?

Explain why computers use binary, describe place value in binary and hexadecimal, and state why hexadecimal is used as shorthand for binary
A focused answer to the O-Level Computing point on number systems. Why computers use binary, place value in binary and hexadecimal, the meaning of bits and bytes, and why hexadecimal is a compact shorthand for binary.
7 min answer →

How are letters, sounds and pictures all stored as binary numbers?

Explain how text (ASCII), sound (sampling) and images (pixels and colour depth) are represented as binary in a computer
A focused answer to the O-Level Computing point on representing data. How text uses character codes such as ASCII, how sound is sampled, and how images are stored as pixels with a colour depth, all as binary.
7 min answer →