A cryogenic storage unit monitor measures temperatures in Kelvin (KKK), which are strictly non-negative. The system uses an 8-bit register to store the temperature as a whole number.
Which of the following explains why the system designer should use an 8-bit unsigned integer rather than an 8-bit two's complement signed integer to record these temperatures?
The 8-bit unsigned integer can represent a maximum temperature of 255 K255\text{ K}255 K, whereas the 8-bit two's complement integer can only represent a maximum positive temperature of 127 K127\text{ K}127 K.
The two's complement representation requires an additional sign bit that reduces the total number of representable states from 256256256 to 128128128.
Unsigned integers are immune to arithmetic overflow when adding positive values, whereas two's complement integers will always overflow if any two values are added.
Two's complement integers cannot represent the absolute zero value (0 K0\text{ K}0 K) because they contain dual representations for zero (+0 and -0).
117 exam-style questions on Edexcel GCSE Computer Science Binary, covering Binary representation and number of states, Unsigned and two's complement integers, Converting denary and 8-bit binary, Binary addition and binary shifts, Concept of overflow, and Hexadecimal notation and conversion. Each one has a worked solution and a mark scheme showing where the marks go.