Arrays/Lists

    AQA
    GCSE

    Arrays and lists are fundamental data structures used to store multiple items under a single identifier, accessible via computed indices. Candidates must distinguish between static, fixed-size arrays (contiguous memory allocation) and dynamic lists, applying appropriate traversal algorithms using iteration. Mastery requires the ability to manipulate data within one-dimensional and two-dimensional structures, implement standard algorithms such as linear search, and accurately trace index values during execution.

    0
    Objectives
    4
    Exam Tips
    4
    Pitfalls
    4
    Key Terms
    5
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for correctly identifying or using the index of a specific element, strictly adhering to zero-based indexing conventions.
    • Credit responses that successfully implement iteration (for/while loops) to traverse an array for searching or processing data.
    • Award marks for correct syntax when accessing 2D array elements, specifically adhering to the `array[row][column]` ordering.
    • Candidates must correctly update a specific element's value without altering the integrity or order of surrounding data.
    • Award 1 mark for initializing an empty list/array correctly before populating it within a loop.

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for correctly identifying or using the index of a specific element, strictly adhering to zero-based indexing conventions.
    • Credit responses that successfully implement iteration (for/while loops) to traverse an array for searching or processing data.
    • Award marks for correct syntax when accessing 2D array elements, specifically adhering to the `array[row][column]` ordering.
    • Candidates must correctly update a specific element's value without altering the integrity or order of surrounding data.
    • Award 1 mark for initializing an empty list/array correctly before populating it within a loop.

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When tracing algorithms involving arrays, explicitly write out the array indices (0, 1, 2...) above the values in the question paper to prevent alignment errors.
    • 💡For 2D arrays, strictly memorize the convention `Array[Row][Column]`—visualize this as 'Down then Across' to ensure accuracy in coordinate mapping.
    • 💡In 'Write' questions, ensure you distinguish between the loop counter (e.g., `i`) and the array element (e.g., `scores[i]`); using the wrong one is a major penalty.
    • 💡Use meaningful variable names for arrays (e.g., `student_scores` rather than `list1`) to aid logic and secure marks for code readability.

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing the index of an element with the data value stored at that index during trace table completion.
    • Off-by-one errors, specifically attempting to access index `n` in an array of length `n` (where the maximum valid index is `n-1`).
    • Reversing row and column indices when accessing two-dimensional arrays, leading to incorrect data retrieval logic.
    • Assuming arrays are automatically sorted when performing binary searches, failing to recognize the precondition.

    Key Terminology

    Essential terms to know

    Likely Command Words

    How questions on this topic are typically asked

    State
    Explain
    Write
    Complete
    Trace
    Compare

    Practical Links

    Related required practicals

    • •{"code":"Standard Algorithm","title":"Linear Search Implementation","relevance":"Iterating through an array to find a target value"}
    • •{"code":"Standard Algorithm","title":"Bubble Sort","relevance":"Swapping array elements based on comparison"}

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