Computing
What the Computing domain tests
The Computing domain checks mathematical reasoning, Boolean logic, number representation, and the ability to trace short algorithms. It is not a test of a particular programming language; pseudocode and clear control-flow reasoning are enough.
Core rules and concepts
- In Boolean algebra, build truth tables row by row; n variables need 2^n rows. De Morgan’s laws convert AND/OR expressions with negation.
- Convert between binary, decimal, and hexadecimal by grouping bits; in two’s complement, the leading bit carries a negative weight.
- Trace loops with a table of variable values. For recursion, identify the base case and the shrinking input.
- Know the difference between O(1), O(log n), O(n), and O(n log n) for common array and search operations.
- In probability and counting, decide whether order matters and whether repetition is allowed before choosing a formula.
Worked example
Trace: x = 0; for i = 1 to 4: x = x + 2i. Reasoning: i = 1, 2, 3, 4 add 2, 4, 6, 8, so x becomes 2, 6, 12, 20. The final value is 20. A common error is to add i instead of 2i, or to run the loop five times by including 0.
Traps that cost marks
Off-by-one loop bounds, integer division truncation, operator precedence, zero-based indexing versus one-based counting, and confusing “best case” with “average case.” In truth tables, do not skip rows where an input is false; false rows often expose the correct answer.