AQA A-Level Computer Science AS Paper 1, June 2025: Question 5

✅ Acceptable Answers (1 Mark Max)

Provide any one of the following explanations:

• Information hiding: Details of how data are actually stored or represented internally are hidden from the user/programmer.
• Composition: New kinds of data objects or structures can be constructed from previously defined types.
• Valid example: Explaining that an abstract data structure is implemented using a simpler underlying structure (e.g., a stack , queue , or binary tree implemented using an array ).

💡 Key Knowledge

Abstraction comes in multiple flavours in AQA Computer Science:

• General Abstraction: Removing unnecessary details and keeping only what is required to solve the problem.
• Data Abstraction: Isolating how a compound data object is used from how it is constructed out of more primitive data objects.
• Abstract Data Types (ADTs): Defined purely by the operations performed on them (e.g., push()/pop() for a stack), while the internal memory layout remains encapsulated.

🧠 Exam Technique & Examiner Insight

• Focus on the prefix "Data": If the question asks for data abstraction, do not just give the textbook definition of general abstraction. Explicitly mention data representation or data structures.
• Use standard phrasing: Stating that "the underlying implementation or representation of the data is hidden from the user" is the safest and clearest way to guarantee this mark.
• Short, targeted sentences: This is a 1-mark question. A single precise sentence earns the mark—do not write long essays where conflicting statements might spoil the mark.

❌ Common Errors to Avoid

• Generic Abstraction: Writing only "removing unnecessary detail" without referencing data or representation will usually score 0 marks.
• Confusing with Functional/Procedural Abstraction: Describing hiding the inner workings of a subroutine or method (e.g., "not knowing how a function works") rather than the data storage itself.
• Vague statements: Writing "making data simpler" or "shortening variables"—these lack technical precision.