Interactive Trace Table Challenge

Put your programming skills to the test with this interactive Trace Table Challenge! Whether you’re learning to code or preparing for your GCSE Computer Science exams, trace tables are one of the most useful techniques for understanding exactly how an algorithm works.

A trace table lets you follow a program one line at a time, recording how the values of variables change as each instruction is executed. By tracing an algorithm step by step, you can predict the program’s output, spot logical errors before writing any code, and develop a much deeper understanding of sequencing, selection (IF statements) and iteration (FOR and WHILE loops).

This interactive activity contains a series of progressively more challenging algorithms. Your task is to complete the trace table by recording the values of variables, the results of conditions and any output produced by the program. If you get stuck, you can watch the built-in animation to see the algorithm execute line by line before having another go yourself.