The figure shows a photograph of a Casio scientific calculator f x - 83 E S (natural display) with annotations added to explain some of the features. The calculator screen at the top, annotated with ‘display’, has three rows. The top row of the screen contains the letter D (white text on black) in the centre, and the word ‘math’ with an upward pointing arrowhead towards the right end. The middle row of the screen has the mathematical text square root 12 multiplied by square root 6 multiplied by square root 3 all over 2 at the left-hand side. The bottom row has the mathematical text 3 square root 6 at the right-hand side. Beneath the display is a row of five blue buttons annotated, from left to right: ‘shift key’; ‘alpha key’; ‘cursor control button’ (this button is much larger and in the centre); ‘mode key’; ‘on key’. Below these are four rows of black buttons (twenty two buttons in total) with the annotation ‘function keys’. At the bottom left of the calculator an array of twelve buttons is annotated with ‘number keys’. To the right of these the red button labelled D E L (written as one word) is annotated with ‘delete key’ and the red button labelled A C (written as one word) is annotated with ‘all clear key’. Below these the multiply, divide, add, subtract keys are annotated with ‘basic operation keys’. Below these the button labelled Ans is annotated with ‘last answer key’ and the button labelled = is annotated with ‘equals key’.