Algorithms
The Problem Before the Program
Why can a computer find one name among a million faster than you can find one among a hundred? Decomposition and abstraction as jobs rather than words, with a figure that splits one problem into three parts you can test separately; sequence, selection and iteration drawn as three real flowcharts, because what separates them is the shape of the path; and the only two algorithms the DfE names (binary search and merge sort) with a figure that actually runs the search, pass by pass, greying out the half it discards and printing the verdict each comparison produces. The centrepiece is annotated pseudocode: eight lines, with the line that breaks the algorithm while still running perfectly pointed at and explained. A band on which extra algorithms each board names and how each one wants efficiency judged, though not by Big O, which the DfE excludes. Ten terms, and the misconceptions that cost marks.