Question 1
Learning objective
Composition: Know how to build a composition abstraction by combining procedures to form compound procedures. Know how to build data abstractions by combining data objects to form compound data, for example tree data structure. 56
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Topic
Abstraction and automation
Subtopic
Composition
Aqa A Level Computer ScienceTheory of computation
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Quick explanation
Composition: Know how to build a composition abstraction by combining procedures to form compound procedures. Know how to build data abstractions by combining data objects to form compound data, for example tree data structure. 56
- This point belongs to Abstraction and automation, especially Composition.
- You need to be able to composition: Know how to build a composition abstraction by combining procedures to form compound procedures. Know how to build data abstractions by combining data objects to form compound data, for example tree data structure. 56.
- Use the linked flashcards and practice questions to check recall, then practise applying the idea in an exam-style answer.
Why it matters
This objective helps connect Composition to exam-style questions, flashcards, and revision notes for Abstraction and automation.
Quick student answer
What is a composition abstraction?
Direct answer
A compound procedure formed by combining procedures
Key terms
- Composition abstraction: An abstraction created by combining components: procedures are combined to form compound procedures, or data objects are combined to form compound data.
- Compound data: Data formed by combining data objects, such as the data in a tree data structure.
Common trap
Confusing procedures with data objects: State that procedures are combined to form compound procedures, whereas data objects are combined to form compound data.
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Related learning objectives
- Problem-solving: Be able to develop solutions to simple logic problems. Be able to check solutions to simple logic problems.
Problem-solving
- Following and writing algorithms: Understand the term algorithm. A sequence of steps that can be followed to complete a task and that always terminates. Be able to express the solution to a simple problem as an algorithm using pseudo-code, with the standard constructs: • sequence • assignment • selection • iteration. Be able to hand-trace algorithms. Be able to convert an algorithm from pseudo- code into high level language program code. 54 Be able to articulate how a program works, arguing for its correctness and its efficiency using logical reasoning, test data and user feedback.
Following and writing algorithms
- Abstraction: Be familiar with the concept of abstraction as used in computations and know that: • representational abstraction is a representation arrived at by removing unnecessary details • abstraction by generalisation or categorisation is a grouping by common characteristics to arrive at a hierarchical relationship of the 'is a kind of' type.
Abstraction
- Information hiding: Be familiar with the process of hiding all details of an object that do not contribute to its essential characteristics.
Information hiding
- Procedural abstraction: Know that procedural abstraction represents a computational method. The result of abstracting away the actual values used in any particular computation is a computational pattern or computational method - a procedure.
Procedural abstraction