Algorithms

Worked examples (9)

• 1Build a full-mark definition of 'algorithm'
• 2Choose the correct flowchart symbol (multiple choice)
• 3Name two ways of representing an algorithm
• 4Explain the difference between an algorithm and a program
• 5Decide which set of instructions is a valid algorithm
• 6Translate a written description into pseudocode
• 7Justify the best representation for a given algorithm
• 8Explain why an algorithm must be finite
• 9Argue that an algorithm is independent of the machine

Model answers (9)

• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response

Worked examples (9)

• 1State the purpose of a simple accumulator algorithm
• 2Predict the output of an algorithm for given data
• 3Distinguish a counter from a running total
• 4Describe how an algorithm works, step by step
• 5State the purpose of an algorithm given as a flowchart
• 6Identify a planted logic error in a given algorithm
• 7Explain why the choice of loop changes the behaviour
• 8Interpret an algorithm containing a nested loop
• 9Compare two algorithms that produce the same output

Model answers (9)

• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response

Worked examples (9)

• 1Design a sequence-only algorithm
• 2Design an algorithm using selection
• 3Design an algorithm using a count-controlled loop
• 4Design a validation loop and justify the loop choice
• 5Design a banded classification with a chain of conditions
• 6Draw a flowchart for a sentinel-controlled loop
• 7Design an algorithm producing two independent results
• 8Justify a design decision against an alternative
• 9Design a complete solution and evaluate its limitations

Model answers (9)

• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response

Worked examples (9)

• 1Trace a sequence with no loop
• 2Trace a count-controlled loop
• 3Trace a WHILE loop including the condition column
• 4Trace a loop containing a selection
• 5Use a trace table to locate a logic error
• 6Trace a nested loop
• 7Explain why tracing finds errors that reading does not
• 8Analyse the limitations of a successful trace
• 9Trace a validation loop with erroneous input

Model answers (9)

• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response

Worked examples (9)

• 1Translate a simple sequence into Python
• 2Translate a selection, watching the comparison operator
• 3Translate a count-controlled loop and fix the range
• 4Implement a post-conditioned loop in a language that lacks one
• 5Find the error introduced during translation
• 6Translate an array traversal
• 7Explain why the same algorithm looks different in two languages
• 8Translate a complete algorithm with validation and a total
• 9Evaluate the choice of programming language for the practical paper

Model answers (9)

• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response

Worked examples (9)

• 1Describe how a linear search works
• 2Trace the first pass of a bubble sort
• 3Explain why binary search needs sorted data
• 4Trace a binary search and count the comparisons
• 5Describe how a merge sort works
• 6Compare a linear search with a binary search
• 7Choose an algorithm for a described situation
• 8Assess bubble sort against merge sort for a given task
• 9Explain how the data itself determines the algorithm

Model answers (9)

• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response

Worked examples (9)

• 1Identify a weakness in a maximum-finding algorithm
• 2Choose test data in all three categories
• 3Suggest a specific improvement
• 4Quantify an efficiency claim
• 5Rank two faults by severity
• 6Design a test plan for a given algorithm
• 7Evaluate an algorithm against its stated requirement
• 8Judge two algorithms against the same requirement
• 9Evaluate what testing can and cannot establish

Model answers (9)

• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — short open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — open-response
• ✓Model answer — Edexcel 4CP0 Paper 1 style — extended open-response