Reading and tracing complex pseudocode

The exact sequence in which an algorithm's lines run, followed step by step to trace its behaviour.

Part of: VCE Pseudo Code — Module 28, 7-8 Digital Technologies: Designing and tracing algorithms — Module 35, ACARA Digital Technologies Years 7–8 — Tracing and Debugging Algorithms — Module 29, WA Computer Science ATAR Year 11 — Pseudocode and Algorithm Design — Module 67

Understanding Reading and tracing complex pseudocode in VCE Pseudocode

What it does: The DISPLAY statement is guarded by the IF condition. Tracing is the technique of manually stepping through code. A nested loop starts fresh every time the outer loop moves on. The inner loop variable j completes its full range before i changes. The DISPLAY statement only executes when j equals 2. Following each step by hand reveals exactly what gets displayed. Skipping lines can lead to an incorrect trace of the algorithm. This is exactly what execution order means.

Common mistakes: DISPLAY i does run - whenever j equals 2. The inner code runs inside the outer loop, not before it.

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This module's key terms are also in a printable crossword (Modules 11–28) and word search (Modules 1–28).

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Learning

Duo

Does tracing follow an algorithm's lines in execution order?

YesNo

Matches

The inner loop never resets between outer passes

↓

Wrong - the inner loop restarts every outer pass

Applying

Meanings

Term

Execution order

Meaning

The exact sequence in which an algorithm's lines run, followed step by step to trace its behaviour.

Practice

BEGIN

Testing

Gaps

The outer loop runs from 1 to

Check Answer

Spots

2The inner loop runs 2 times

3DISPLAY i never runs at all

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Quick Questions

1. Does tracing follow an algorithm's lines in execution order?

A. Yes ✓

B. No

Tracing means stepping through the code exactly as it runs.

2. Does the inner loop reset each time the outer loop advances?

A. No

B. Yes ✓

A nested loop starts fresh every time the outer loop moves on.

3. In this example, does j change faster than i?

A. No

B. Yes ✓

The inner loop variable j completes its full range before i changes.

4. Does DISPLAY i run only when the IF condition is true?

A. Yes ✓

B. No

The DISPLAY statement only executes when j equals 2.

5. Can tracing help predict an algorithm's final output?

A. Yes ✓

B. No

Following each step by hand reveals exactly what gets displayed.

Match the Pairs

Execution order → The exact sequence in which an algorithm's lines run

FOR j FROM 1 TO 2 → The inner loop that resets each outer pass

Runs only when j equals 2 → DISPLAY i

Following code by hand to predict its output → Tracing

The inner loop never resets between outer passes → Wrong - the inner loop restarts every outer pass

Tracing can skip lines to save time → Wrong - tracing must follow every line in order

Key Term

Execution order

The exact sequence in which an algorithm's lines run, followed step by step to trace its behaviour.

Fill in the Blanks

1. The outer loop runs from 1 to 3

Hint: Type the final value of the outer loop counter.

2. The inner loop runs from 1 to 2

Hint: Type the final value of the inner loop counter.

3. DISPLAY i runs when j = 2

Hint: Type the comparison operator used to check equality.

4. Trace tables help follow execution

Hint: Type the word for tracking each step in order.

5. Nested loops run the inner code repeatedly

Hint: Type the word for the loop found inside another loop.

Spot the Error

Question 1

A The outer loop runs 3 times

B The inner loop runs 2 times

C DISPLAY i never runs at all

Line C — DISPLAY i does run - whenever j equals 2.

Question 2

A FOR i FROM 1 TO 3

B FOR j FROM 1 TO 2

C IF j = 2 THEN

D This runs before the outer loop

Line D — The inner code runs inside the outer loop, not before it.

Question 3

A i counts the outer passes

B j never resets each outer pass

C j counts the inner passes

Line B — j does reset to 1 at the start of each outer pass.

Question 4

A DISPLAY i shows j's value

B IF j = 2 THEN checks a value

C DISPLAY i shows i's value

D j resets each outer pass

Line A — DISPLAY i shows the value of i, not j.

Question 5

A The algorithm has two loops

B One loop is nested inside another

C j resets on each outer pass

D DISPLAY runs when j equals 2

E Tracing ignores loop order

Line E — Tracing must follow the exact order the loops execute in.

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