Tracing algorithms
Lesson details
Learning outcome
I can use trace tables to test the logic of an algorithm.
Key learning points
- Trace tables can be used to walkthrough and understand the logic of an algorithm.
- Trace tables can be used to help find logical errors in algorithms.
Keywords
Trace table - a tool used to track the values of variables and the flow of execution in an algorithm or program, step by step
Error - a mistake or unexpected behaviour in a program that prevents it from working correctly
Modulo - an operation that gives you the remainder when one number is divided by another
Common misconception
Using trace tables guarantees correct logic and code.
Trace tables can be subject to human error and can be impractical to use for complex algorithms.
Teacher tip
Initially, pupils can struggle to keep track of variable changes in trace tables. Model the completion of trace tables slowly by narrating the changes as they happen.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What is a set of step-by-step instructions to solve a problem called?
Q2.Why is it helpful to develop an algorithm’s logic before coding?
Q3.What is a diagram that represents logic or data (or similar alternatives)?
Q4.What does decomposition involve?
Q5.What is abstraction in computational thinking?
Q6.What is a way to express an algorithm in plain language (or similar alternatives)?
Assessment exit quiz
6 Questions
Q1.Match the terms with their definitions.
a tool to track variable values and execution flow
a mistake in a program that prevents it from working correctly
an operation that gives the remainder when dividing two numbers
mistakes made by people when creating trace tables
the process of running an algorithm or program
Q2.What is a trace table used for?
Q3.What is a common limitation of trace tables?
Q4.What is the result of 10%3?
Q5.Arrange these steps into the correct order for creating a trace table.
Q6.Why might trace tables be impractical for complex algorithms?
To help you plan your 10 computer science lesson on: Tracing algorithms, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 computer science lesson on: Tracing algorithms, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
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Explore more key stage 4 computer science lessons from the Algorithms unit, dive into the full secondary computer science curriculum, or learn more about lesson planning.