Programming

Programming is the largest unit in GCSE Computer Science, covering variables and constants, data types, operators, selection, iteration, arrays, records, subroutines, parameters, scope, validation, testing and robust programming.

Work through it in order, since each topic builds on the last. Selection and iteration must be secure before nesting them, and arrays only become useful once loops are comfortable. Indexing is a persistent source of error: strings and arrays start at zero, so an array of eight elements has a last index of seven, and two-dimensional arrays take the row before the column. Subroutines connect back to decomposition and are examined alongside it. Testing questions expect all three data types, and boundary data in particular, since off-by-one errors cluster at the limits of a range.