Writing exam answers about decomposition and abstraction
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Which answer defines decomposition correctly?
2. Which answer defines abstraction correctly?
3. Which exam answer would earn the reason mark for 'Explain why decomposition is useful'?
4. A student writes: 'Decomposition makes testing easier because each sub-system can be tested on its own.' What is good about this answer?
5. A question asks you to list the inputs for a program that calculates the area of a rectangle. Which answer is correct?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1Decomposition is breaking a problem into smaller sub-problems. | AThis gives a point but no reason. It needs a 'because' to explain why, such as because smaller parts are easier to understand and test. | |
| 2Abstraction is removing unnecessary detail and keeping the important parts. | BThis confuses abstraction with decomposition. Breaking a problem into parts is decomposition, while abstraction is removing unnecessary detail. | |
| 3A full-mark answer links each point to a reason, for example by using the word 'because'. | CA correct one-sentence definition of decomposition that uses the key term accurately. | |
| 4A full-mark answer for a scenario lists the input, process, output and storage using the correct terms. | DInput: score. Process: add to total. Output: display total. Storage: save to file. | |
| 5Abstraction is breaking a problem into smaller sub-problems. | EA correct one-sentence definition of abstraction that uses the key term accurately. | |
| 6Decomposition makes a problem easier to solve. | FDecomposition makes the problem easier because each sub-system can be solved and tested separately. |
C
Definitions
full-mark answer
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
_____________ means breaking a problem
down into smaller sub-problems.
2.
___________ removes unneeded detail to
focus on the important features.
3.
Decomposition makes it easier _______ each
sub-system can be tested separately.
4.
The four parts are input, process, output
and _______.
5.
Removing detail is abstraction,
not _____________.
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
Decomposition splits a problem
B
into smaller sub-problems.
C
This helps and each part
D
is easier to solve.
Question 2
A
Abstraction removes unneeded
B
detail and keeps all features.
C
It makes a problem simpler.
Question 3
A
Two key terms are different.
B
Decomposition = hiding detail
C
Abstraction = hiding detail
Question 4
A
Scenario: a quiz app
B
Input: player's answer
C
Output: compare with correct
D
Output: right or wrong message
E
Storage: high score file
Question 5
A
Scenario: library loans
B
Input: book ID and member ID
C
Process: check the book is in
D
Process: loan receipt printed
E
Storage: loan records file
Answer Key
Writing exam answers about decomposition and abstraction
Section A: Quick Questions
Q1
B — Breaking a complex problem down into smaller, more manageable sub-problems
Q2
B — Keeping only the details needed to solve the problem and ignoring the rest
Q3
A — It makes the problem easier to solve because each smaller sub-problem can be tackled separately
Q4
A — It uses a key term and links the point to a reason
Q5
A — The length and the width entered by the user
Section B: Match the Pairs
Q1
Decomposition is breaking a problem into smaller sub-problems. → A correct one-sentence definition of decomposition that uses the key term accurately.
Q2
Abstraction is removing unnecessary detail and keeping the important parts. → A correct one-sentence definition of abstraction that uses the key term accurately.
Q3
A full-mark answer links each point to a reason, for example by using the word 'because'. → Decomposition makes the problem easier because each sub-system can be solved and tested separately.
Q4
A full-mark answer for a scenario lists the input, process, output and storage using the correct terms. → Input: score. Process: add to total. Output: display total. Storage: save to file.
Q5
Abstraction is breaking a problem into smaller sub-problems. → This confuses abstraction with decomposition. Breaking a problem into parts is decomposition, while abstraction is removing unnecessary detail.
Q6
Decomposition makes a problem easier to solve. → This gives a point but no reason. It needs a 'because' to explain why, such as because smaller parts are easier to understand and test.
Section C: Definitions
Q1
full-mark answer — Uses key terms (sub-system, decomposition, abstraction, input, process, output, storage) correctly and gives a reason for each point, for example by using the word 'because'.Section D: Fill in the Blanks
Q1
Decomposition means breaking a problem
down into smaller sub-problems.Q2
Abstraction removes unneeded detail to
focus on the important features.Q3
Decomposition makes it easier because each
sub-system can be tested separately.Q4
The four parts are input, process, output
and storage.Q5
Removing detail is abstraction,
not decomposition.Section E: Spot the Error
Q1
C — The sentence gives no reason. A full-mark answer links the point with 'because', for example 'This helps because each part is easier to solve.'
Q2
B — Abstraction keeps only the key features, not all of them. The line should say 'detail and keeps key features.'
Q3
B — This confuses decomposition with abstraction. Decomposition means splitting a problem into smaller parts, so the line should be 'Decomposition = splitting up'.
Q4
C — Comparing the answer with the correct one is a process, not an output. The line should start 'Process:'.
Q5
D — A printed receipt is shown to the user, so it is an output, not a process. The line should start 'Output:'.