These are original Marlbridge practice questions, not past exam questions. All scenarios are fictional. The code is Marlbridge’s rendering of the exam reference notation (← assignment, = equality test, lists start at index 1, DISPLAY shows a value). Mark points are a suggested Marlbridge rubric, not an official scoring guideline. No calculator is needed or allowed. Try each question before opening its answer.
Question 1 (multiple choice · foundation)
Which statement best describes an algorithm?
- (A) The result a program displays when it is run.
- (B) A finite set of instructions that accomplish a specific task.
- (C) A list of all the variables used in a program.
- (D) A program written in a specific programming language.
Answer and explanation
Answer: (B). An algorithm is defined by what it does, not by the language it is in.
- (A) Output is a result, not the algorithm.
- (C) Variables are part of a program, not its definition.
- (D) A program can implement an algorithm, but an algorithm can also be written as natural language or a diagram.
Question 2 (multiple choice · core)
Algorithm 1 is IF(n MOD 2 = 0) { r ← true } ELSE { r ← false }. Which of these stores the same value in r for every whole number n ≥ 0?
- (A)
r ← NOT(n MOD 2 = 0) - (B)
r ← (n MOD 2 = 0) - (C)
r ← (n MOD 2 = 1) - (D)
r ← (n / 2 = 0)
Answer and explanation
Answer: (B). Both store whether the remainder is 0.
- (A) is the negation, so it disagrees on every input.
- (C) stores whether n is odd: the opposite.
- (D) is true only for n = 0.
Question 3 (multiple choice · core)
What does Algorithm D (two separate IF statements, one testing x > y and one testing y > x) store in big when big starts at 0 and both x and y are 4?
big ← 0
x ← 4
y ← 4
IF(x > y)
{
big ← x
}
IF(y > x)
{
big ← y
}
DISPLAY(big)- (A) 0
- (B) 8
- (C) 4
- (D) An error occurs.
Answer and explanation
Answer: (A). Neither condition is true when the two numbers are equal, so big is never assigned and keeps its starting value of 0.
- (B) nothing adds the numbers.
- (C) is what an IF … ELSE version would give.
- (D) The code is valid; it simply does not change
big.
Question 4 (multiple choice · core)
What is displayed?
a ← 9
b ← 2
c ← 4
big ← a
IF(b > big)
{
big ← b
}
IF(c > big)
{
big ← c
}
DISPLAY(big)- (A) 4
- (B) 9
- (C) 2
- (D) 15
Answer and explanation
Answer: (B). big starts at 9. b > big (2 > 9) is false and c > big (4 > 9) is false, so big stays 9.
- (A) and (C) are the other numbers, which would be chosen only if they were larger.
- (D) is the sum.
Question 5 (multiple choice · foundation)
A programmer wants a program that displays the average of four test scores. Which existing algorithm should be reused as part of the solution?
- (A) Finding a robot’s path through a maze
- (B) Testing whether an integer is divisible by another
- (C) Finding the minimum of two numbers
- (D) Computing the sum of the numbers
Answer and explanation
Answer: (D). An average is a sum divided by the count, so the sum algorithm is the building block.
- (A) is unrelated.
- (B) answers a divisibility question.
- (C) gives the lowest score, not the average.
Question 6 (multiple choice · core)
Which is a benefit of building a new algorithm from existing, correct algorithms?
- (A) It guarantees the new algorithm is the fastest possible.
- (B) It reduces testing and simplifies finding errors.
- (C) It removes the need to understand what the existing algorithm does.
- (D) It makes the algorithm independent of the programming language.
Answer and explanation
Answer: (B). Trusted parts need less testing, and a fault is more likely to be in the new part.
- (A) Reuse does not guarantee speed.
- (C) You still need to understand what the part does.
- (D) The algorithm still has to be written in some language or notation.
Question 7 (multiple select, choose two · foundation)
Which two of these are ways to express an algorithm without using a programming language?
- (A) A running application
- (B) A compiled program
- (C) Natural language steps
- (D) A flowchart
- (E) Machine code
Answer and explanation
Answers: (C) and (D). Natural language and diagrams such as flowcharts are language-free.
- (A), (B) and (E) are program forms that a computer runs.
Question 8 (constructed response · core)
Using the “largest of three” and “smallest of three” code from the guide as a starting point, write code that stores in spread the difference between the largest and smallest of a, b and c, and displays it. Trace it for a = 3, b = 8, c = 8.
Answer and explanation
One correct answer:
big ← a
IF(b > big)
{
big ← b
}
IF(c > big)
{
big ← c
}
small ← a
IF(b < small)
{
small ← b
}
IF(c < small)
{
small ← c
}
spread ← big - small
DISPLAY(spread)Trace for 3, 8, 8: big starts at 3; 8 > 3 so big is 8; 8 > 8 is false, so big stays 8. small starts at 3; 8 < 3 false; 8 < 3 false; small stays 3. spread is 8 − 3 = 5, so 5 is displayed. The tie between b and c causes no problem.
Suggested Marlbridge rubric (5 marks)
| Mark point | Marks |
|---|---|
| Largest of the three computed correctly | 1 |
| Smallest of the three computed correctly (uses < not >) | 1 |
| Combines them with big - small and displays it | 1 |
| Trace shows big = 8, small = 3 | 1 |
| Result 5, and comments on the tie | 1 |
Question 9 (constructed response · core)
A shop gives free delivery when the order total is 100 or more. Two programmers write: Algorithm P IF(total ≥ 100) { free ← true } ELSE { free ← false } and Algorithm Q IF(total > 100) { free ← true } ELSE { free ← false }. (a) Give one value of total for which they give different results and state each result. (b) Which algorithm matches the requirement? (c) Write a one-line replacement for P that uses no IF statement.
Answer and explanation
(a) total equal to 100. P gives true because 100 ≥ 100. Q gives false because 100 > 100 is false.
(b) P matches “100 or more”, because the boundary value 100 must qualify.
(c) free ← (total ≥ 100).
Suggested Marlbridge rubric (4 marks)
| Mark point | Marks |
|---|---|
| (a) Identifies 100 as the differing input | 1 |
| (a) Correct result for each algorithm | 1 |
| (b) Chooses P with the boundary reason | 1 |
| (c) A correct Boolean assignment with no IF | 1 |
How did you do?
Count the questions you got right first time, then read the explanation for every one you missed, including the wrong options you rejected correctly, because the distractors show you the typical slips. Anything you missed twice goes onto your revision list for the revision notes; re-read the matching section of the study guide before trying again.