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OCR H446 2.3.1 Designing and representing algorithms

Part 1 of 16 · H446 2.3.1 · Algorithms

OCR H446 2.3.1 opens with algorithm design, where students must produce finite, testable steps and then move the same logic between a flowchart, pseudocode and program code. This worksheet builds that habit from the start, so students learn that changing the notation must never quietly change what the algorithm does.

Students will:

  • separate a problem statement into inputs, validation, processing and outputs
  • rewrite the same logic as pseudocode and describe how its decisions appear in a flowchart
  • keep decision, loop-back and update order identical across representations
  • design an algorithm for an unfamiliar charging rule with a cap and a rejection condition
  • choose normal, boundary and invalid test cases with expected outputs

Inside: 6 explanation cells, 1 multiple-choice question, 1 fill-in-the-blanks cell and 2 written answers. 20 marks, about 20 to 30 minutes.

Series: H446 2.3.1 · Algorithms, part 1 of 16.

Shared by Coding PathwayVerified teacher

  • 10 cells
  • About 30 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 3 Sept 2026

Preview

The whole resource, exactly as a class sees it. Answers and marking are held back.

Designing and representing algorithms

Algorithms turn precise requirements into finite steps. Representation changes how we communicate the logic; it does not change what the logic must do.

By the end, you will be able to

  • define inputs, outputs, validation and processing;
  • decompose a problem into testable stages;
  • express the same algorithm as flowchart, pseudocode and code;
  • justify a representation for an audience and purpose.

Reactivate: sequence, selection and iteration are control structures.

Model before notation

From problem to algorithm representationProblem andrequirementsValidate inputProcess dataProduce outputFlowchartPseudocodeProgram codeSame logic;different notation

Worked requirement: accept positive journey times until -1, then output their mean. Inputs are repeated numbers plus sentinel; validation rejects non-positive values except -1; processing accumulates total/count; output divides only when count is non-zero.

Multiple choice1 mark

Which addition makes the journey-time algorithm unambiguous?

  • ARepeat until -1 is entered
  • BUse a nice screen
  • CProcess some values
  • DShow the answer quickly

Worked translation

Pseudocode may say WHILE time <> -1, whereas Python says while time != -1:. A flowchart uses a decision diamond. In each, the decision, loop-back and update order must match. Test normal, boundary and invalid inputs before coding.

Written answer6 marks

Decompose an algorithm that accepts five marks from 0 to 100 and outputs the highest mark. Specify input, validation, processing, output and two tests.

Use precise conditions and expected results.

Students type their answer here.

Independent transfer

Design an algorithm for a library fine: input days late and member status; reject negative days; members pay 20p/day, others 30p/day; cap the fine at £10; output the amount.

Written answer9 marks

Write precise pseudocode and explain how its decisions would appear in a flowchart. Include three test cases with expected outputs.

Check validation, selection order and cap boundary.

Students type their answer here.

Closed-book checkpoint

Complete each sentence from memory. There is no answer bank and correctness is held for teacher review.

Fill in the blanks4 marks
A finite sequence of unambiguous steps is an completion 1. A diagram using standard process and decision shapes is a completion 2. A language-independent structured description is completion 3. An executable implementation is completion 4.

Review your understanding

Before submitting, check that you can explain the central distinction in your own words, expose the intermediate state that supports your answer and apply the method in an unfamiliar context.