← IGCSE Computer Science Paper 2

Indentation and comments in pseudocode

Starts a comment in Cambridge pseudocode. Statements inside a loop or IF are indented four spaces, and ELSE lines up with its IF, so the structure is easy to read.

Part of: IGCSE Computer Science 0478 — 8.1b Sequence, Selection and Iteration — Module 5

Understanding Indentation and comments in pseudocode in IGCSE Computer Science Paper 2

What it does: OUTPUT Count is the loop body and is indented four spaces, while FOR and NEXT stay at the left. Cambridge pseudocode starts a comment with //. The # symbol is used for comments in Python, not in Cambridge pseudocode. A comment needs two slashes, //. A single / is not a comment, so the line would cause an error. Everything after // is a comment. In the wrong answer the // comes first, so the assignment is turned into a comment and never runs. Indentation and comments help people read the algorithm. Comments are ignored when the algorithm is followed.

Common mistakes: A comment after a statement starts with //, not #. The line should be ' total <- total + n // add'. Cambridge pseudocode comments start with //. The /* ... */ style belongs to other languages. The line should be ' // count down by one'.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 358–368) and word search (Modules 358–378).

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Learning

Duo

Which symbol starts a comment in Cambridge pseudocode?

//#

Matches

FOR Count <- 1 TO 3 OUTPUT Count NEXT Count

↓

The loop body is not indented. OUTPUT Count should be indented four spaces so it is clearly inside the loop.

Applying

Meanings

Term

Meaning

Starts a comment in Cambridge pseudocode. Statements inside a loop or IF are indented four spaces, and ELSE lines up with its IF, so the structure is easy to read.

Practice

// Count the passes

Testing

Gaps

Ask the user for a name

Check Answer

Spots

3 INPUT n

4 total <- total + n # add

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Quick Questions

1. Which symbol starts a comment in Cambridge pseudocode?

A. // ✓

B. #

Cambridge pseudocode starts a comment with //. The # symbol is used for comments in Python, not in Cambridge pseudocode.

2. How far are the statements inside a FOR loop indented?

A. Not indented, lined up with FOR

B. Four spaces in from the FOR line ✓

The body of a loop is indented four spaces. This shows which statements are repeated.

3. Where should ELSE be placed in an IF statement?

A. Lined up with its IF ✓

B. Indented four spaces under the IF

ELSE lines up with its IF. Only the statements inside each branch are indented four spaces.

4. Which is a correct comment on its own line?

A. / Ask the user for a mark

B. // Ask the user for a mark ✓

A comment needs two slashes, //. A single / is not a comment, so the line would cause an error.

5. Which line has a correct comment after a statement?

A. Count <- Count + 1 // add one to count ✓

B. // Count <- Count + 1 add one to count

Everything after // is a comment. In the wrong answer the // comes first, so the assignment is turned into a comment and never runs.

Match the Pairs

// Add the mark to the total → A comment on its own line. The computer ignores it; it explains the code to a human reader.

Total <- Total + Mark // running total → A comment after a statement. The assignment still runs and everything after // is ignored.

The body of a FOR loop is indented four spaces so the repeated statements stand out → FOR Count <- 1 TO 5 OUTPUT Count NEXT Count

ELSE lines up with its IF, and the statements in each branch are indented four spaces → IF Mark >= 50 THEN OUTPUT "Pass" ELSE OUTPUT "Fail" ENDIF

FOR Count <- 1 TO 3 OUTPUT Count NEXT Count → The loop body is not indented. OUTPUT Count should be indented four spaces so it is clearly inside the loop.

IF Age >= 16 THEN OUTPUT "Adult" ELSE OUTPUT "Child" ENDIF → ELSE is indented. It should line up with its IF at the left edge.

Key Term

//

Starts a comment in Cambridge pseudocode. Statements inside a loop or IF are indented four spaces, and ELSE lines up with its IF, so the structure is easy to read.

Fill in the Blanks

1. // Ask the user for a name INPUT Name

Hint: Type the symbol that starts a comment line in Cambridge pseudocode.

2. FOR Count <- 1 TO 5 OUTPUT Count // show the number NEXT Count

Hint: Type the symbol that starts a comment placed after a statement.

3. IF Mark >= 50 THEN OUTPUT "Pass" ENDIF

Hint: Type the indentation (spaces) for a statement inside the IF.

4. WHILE Num > 0 DO Num <- Num - 1 ENDWHILE

Hint: Type the keyword that closes the loop, lined up with its WHILE.

5. FOR Count <- 1 TO 3 // Print the count OUTPUT Count

Hint: Type the symbol that starts a comment on its own line inside the loop body.

Spot the Error

Question 1

A total <- 0

B FOR i <- 1 TO 5

C INPUT n

D total <- total + n # add

E NEXT i

Line D — A comment after a statement starts with //, not #. The line should be ' total <- total + n // add'.

Question 2

A WHILE n > 0 DO

B /* count down by one */

C n <- n - 1

D ENDWHILE

Line B — Cambridge pseudocode comments start with //. The /* ... */ style belongs to other languages. The line should be ' // count down by one'.

Question 3

A IF age >= 16 THEN

B OUTPUT "Adult"

C ELSE THEN

D OUTPUT "Child"

E ENDIF

Line C — ELSE stands on its own line, lined up with its IF. Only IF takes THEN. The line should be 'ELSE'.

Question 4

A REM Add up five marks

B total <- 0

C FOR i <- 1 TO 5

D total <- total + i

E NEXT i

Line A — Cambridge pseudocode starts a comment with //, not REM. The line should be '// Add up five marks'.

Question 5

A IF score > 50 THEN

B / score is a pass

C OUTPUT "Pass"

D ENDIF

Line B — A comment needs two slashes, //. A single / would be read as code. The line should be ' // score is a pass'.

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