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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 programs manipulate individual bits, and what are masks and shifts used for?

Apply bitwise AND, OR, XOR, NOT and shift operations, and use masks to set, clear, toggle and test individual bits
A focused answer to the H2 Computing outcome on bitwise operations. The AND, OR, XOR and NOT operators, left and right shifts, and using masks to set, clear, toggle and test individual bits.
8 min answer →

How are text characters stored as numbers, and why did the world move from ASCII to Unicode?

Explain how characters are encoded using ASCII and Unicode, including code points and UTF-8, and the implications for storage and internationalisation
A focused answer to the H2 Computing outcome on character encoding. ASCII and its limits, Unicode code points, the UTF-8 variable-length scheme, and the implications for storage and supporting many languages.
7 min answer →

How do computers store fractional and very large numbers, and why is floating-point arithmetic only approximate?

Explain floating-point representation in terms of sign, mantissa and exponent, and discuss precision, range and rounding error
A focused answer to the H2 Computing outcome on floating point. The sign, mantissa and exponent fields, normalisation, the trade-off between precision and range, and why rounding errors arise.
8 min answer →

How do computers represent numbers in binary and hexadecimal, and how do we convert between bases reliably?

Convert whole numbers between binary, denary and hexadecimal, and perform binary addition, explaining the role of place value and overflow
A focused answer to the H2 Computing outcome on number bases. Place value in binary and hexadecimal, conversion methods between binary, denary and hexadecimal, binary addition, and the meaning of overflow.
8 min answer →

How do computers store negative whole numbers, and why is two's complement the standard scheme?

Represent signed integers using two's complement, convert to and from denary, and perform subtraction by addition, explaining range and overflow
A focused answer to the H2 Computing outcome on signed integers. Two's complement encoding, converting to and from denary, subtraction as addition, the representable range, and detecting signed overflow.
8 min answer →