ExpertEasy1 markMultiple Choice
AQA GCSE · Question 02.1 · Fundamentals of algorithms
Figure 2 shows an algorithm that uses integer division which has been represented using pseudo-code. Line numbers are included but are not part of the algorithm.
Figure 2
1 again ← True
2 WHILE again = True
3 a ← USERINPUT
4 IF a > 0 THEN
5 counter ← 0
6 WHILE a > 0
7 a ← a DIV 3
8 counter ← counter + 1
9 ENDWHILE
10 ELSE
11 again ← False
12 ENDIF
13 OUTPUT a
14 ENDWHILE
Where is iteration first used in the algorithm in Figure 2?
Figure 2 shows an algorithm that uses integer division which has been represented using pseudo-code. Line numbers are included but are not part of the algorithm.
Figure 2
1 again ← True
2 WHILE again = True
3 a ← USERINPUT
4 IF a > 0 THEN
5 counter ← 0
6 WHILE a > 0
7 a ← a DIV 3
8 counter ← counter + 1
9 ENDWHILE
10 ELSE
11 again ← False
12 ENDIF
13 OUTPUT a
14 ENDWHILE
Where is iteration first used in the algorithm in Figure 2?
Answer options:
A.
Line number 2
B.
Line number 4
C.
Line number 6
D.
Line number 11
How to approach this question
1. Understand the term "iteration". Iteration refers to the repetition of a block of code. Common iteration structures are `FOR` loops and `WHILE` loops.
2. Scan the code in Figure 2 from top to bottom.
3. Line 2 contains `WHILE again = True`. This is the beginning of a loop.
4. Line 6 also contains a `WHILE` loop, but since it appears after line 2, the loop on line 2 is the first instance of iteration in the algorithm.
Full Answer
A.Line number 2✓ Correct
In programming, there are three basic control structures: sequence, selection, and iteration.
- **Sequence:** Instructions are executed one after another.
- **Selection:** A choice is made between different paths of execution (e.g., `IF-THEN-ELSE`).
- **Iteration:** A block of code is executed repeatedly (e.g., `WHILE` loops, `FOR` loops).
The question asks for the first use of iteration. The `WHILE` loop on line 2 is the first iterative construct in the algorithm. The `IF` statement on line 4 is selection. The `WHILE` loop on line 6 is also iteration, but it occurs after the one on line 2.
Common mistakes
✗ Confusing selection (`IF` statements) with iteration (`WHILE` loops).\n✗ Identifying the second loop (line 6) instead of the first one (line 2).
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