Program Development: Algorithms

Lesson objectives

By the end of the week, learners should be able to:

1. Define an algorithm and state why precision matters.
2. Name three algorithm types: sequential, selection and iteration.
3. Write a simple algorithm solving one computational problem.
4. Trace an algorithm step by step and predict the output.
5. Explain why algorithms are the foundation of program development.

Key vocabulary

• Algorithm: a finite sequence of precise instructions solving one problem.
• Precision: the exactness of each instruction in the sequence.
• Sequential algorithm: a list of steps carried out in order.
• Selection algorithm: an algorithm containing if-then-else branches.
• Iteration algorithm: an algorithm repeating steps under a condition.
• Trace: predicting results by stepping through code.
• Foundation: the underlying basis supporting further work.
• Computational problem: a task amenable to algorithmic solution.

Common misconceptions

• "An algorithm is a finished answer." An algorithm is the procedure; the answer comes after running it.
• "Algorithms always use loops." Sequential algorithms solve problems without repetition.
• "An algorithm can change halfway through." Algorithms are complete before execution begins.

Teacher activities

1. Starter: present a problem "calculate the average of five numbers" and ask how to start solving it.
2. Define an algorithm and emphasize precision in every step.
3. Walk through writing a simple algorithm for averaging five numbers.
4. Trace the algorithm step by step on paper.
5. Explain why algorithms are the foundation of program development.
6. Close with the trace task and exit question.

Student activities

1. Read the starter problem and write the first step of an algorithm in their own words.
2. Define an algorithm in their own words and emphasise precision.
3. Write a simple algorithm for calculating an average of five numbers.
4. Trace the algorithm step by step and predict the output.
5. Explain why algorithms are the foundation of program development in one paragraph.
6. Answer the exit question comparing algorithms with finished answers in one sentence.

Practical / learning evidence

A written algorithm with precise steps, a step-by-step trace and an algorithm-foundation explanation. Submit all three for marking.

Resources and preparation

Blank algorithm worksheets, sample number lists and numbered step cards. Offline route: paper versions, no device needed. Display worked examples carefully and avoid letting learners modify them before tracing.

Assessment for learning

Inspect the algorithm for precise, numbered steps with termination. Mark the trace for matching the stated inputs and outputs. Ask a learner to describe the foundation role in one sentence. Flag any learner who thinks algorithms produce answers directly.

Inclusion and homework

Provide the algorithm template prefilled for the first step and allow oral completion of the rest. Extend confident learners with two algorithms and a second homework writing a selection algorithm for pass/fail scoring. Homework: write a second algorithm solving a different computational problem and compare the two approaches.