Structuring Your Responses

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Notes

General Approach to Programming Questions

Programming questions appear in both Paper 1 (algorithm understanding) and Paper 2 (design, write, test, refine).
Paper 2 includes a fixed **15-mark programming question** at the end.
Answers must be in **CIE pseudocode**, Structured English, or a high-level language.
Before writing a program, ask five key questions: inputs, outputs, processes, constructs, subprograms.

Five Key Questions for Programming

**What are the inputs?** – Identify data the program receives (e.g., user input, file).
**What are the outputs?** – Determine what the program displays or saves.
**What processes take place?** – Describe the transformations or calculations.
**What constructs will I need?** – Choose sequence, selection (IF), iteration (WHILE, FOR), assignment, string operations.
**Do I need to use subprograms?** – Use built-in functions (e.g., SUBSTRING, LCASE) or user-defined procedures/functions.

Example: String Manipulation Question

Question: store a string, extract a substring, output lowercase.
Use **SUBSTRING(Quote, Start, Number)** – returns Number chars from position Start (1-indexed).
Use **LCASE(Quote)** to convert to lowercase.
Answer: assign Quote, set Start=25, Number=8, OUTPUT SUBSTRING, OUTPUT LCASE.

What is a Trace Table?

A **trace table** tracks variable values as a program runs line by line.
Tests ability to simulate code and record outputs accurately.
Typically worth **3–6 marks**, often involving iteration, selection, and arrays/lists.
The table structure is usually provided; you fill in missing values.

Command Words for Trace Table Questions

**Complete** – Fill in the table with correct values.
**State** – Give a single value/output/result.
**Explain** – Say why something happens or changes.
**Identify** – Spot where something goes wrong or doesn't match expectations.

Steps to Tackle a Trace Table

**1. Read the code carefully** – Understand loops, IF statements, variable changes.
**2. Use the trace table provided** – Headings and row count guide iterations.
**3. Work line by line** – Simulate in head/paper, update each variable after every change.
**4. Watch for variable resets** – Variables inside loops reset each iteration.
**5. Show final output clearly** – Write exactly as it would appear on screen.

Trace Table Worked Example

Algorithm: total=0, count=1, WHILE count≤3: input number, IF number>10 THEN total+=number, count+=1, OUTPUT total.
Inputs: 12, 8, 15. Output: 27.
Trace table rows: line number, count, number, total, output.
Use a dash (–) when a column is not relevant; keep neat.

Common Mistakes and Tips

**Read code exactly as a computer would** – don't skip lines.
Use a pencil and annotate each step.
Don't fill in lines that just mark end of IF/WHILE (e.g., line 7, 9).
If only 5–6 rows used, something is likely missing.

Example series circuit with cell, switch, lamp, and ammeter.

Particle arrangement in solid, liquid, and gas states.

Practice questions

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1.What is the purpose of a trace table in computer science?
Easy
- ATo follow the values of variables as a program runs
- BTo draw a diagram of the program's structure
- CTo convert high-level code to machine code
- DTo store the program's output
2.In the context of trace tables, what does the command word 'Complete' mean?
Medium
- AFill in the table with correct values
- BGive the value/output/result
- CSay why something happens or changes in the program
- DSpot where something goes wrong or doesn't match expectations
3.Which of the following is NOT a question you should ask yourself when attempting a programming question?
Easy
- AWhat are the inputs?
- BWhat are the outputs?
- CWhat is the file size?
- DWhat constructs will I need to use?
4.In CIE pseudocode, which function is used to convert a string to lowercase?
Easy
- ALCASE()
- BUPPERCASE()
- CLOWER()
- DTOLOWER()
5.Given the string Quote = 'Learning Never Exhausts The Mind', what is the result of SUBSTRING(Quote, 25, 8)?
Medium
- A'The Mind'
- B'The Min'
- C'he Mind'
- D'The Mind' (including the space)
6.In a trace table, what is a common mistake that students make?
Hard
- ASkipping or misreading a line
- BUsing too many rows
- CWriting the output first
- DUsing a pencil
7.In the trace table worked example with inputs 12, 8, 15, what is the final output?
Medium
- A27
- B35
- C20
- D12
8.When completing a trace table, why should you use a new row whenever a variable or output changes?
Hard
- ATo accurately track each step of the program's execution
- BTo make the table look longer
- CTo avoid using too many rows
- DTo confuse the examiner

Slides

Structuring Your Responses

In CIE IGCSE Computer Science, you need to structure your answers clearly for programming and trace table questions.
Programming questions appear in both Paper 1 (understanding algorithms) and Paper 2 (writing and testing programs).
Trace table questions test your ability to simulate code line by line and record variable changes accurately.

Five Key Questions for Programming Questions

When writing a program, always ask: What are the inputs? What are the outputs?
What processes take place? What constructs (sequence, selection, iteration) will I need?
Do I need to use subprograms (built-in functions or user-defined procedures)?

Which of the following is NOT one of the five key questions to ask when answering a programming question?

What are the inputs?
What are the outputs?
What is the colour of the output?
What constructs will I need to use?

Example: String Manipulation Question

Given SUBSTRING(Quote, Start, Number) returns a substring starting at position Start with length Number.
First character is at position 1.
Task: store 'Learning Never Exhausts The Mind' in Quote, extract and display 'The Mind', and output the original string in lowercase.

To extract 'The Mind' from 'Learning Never Exhausts The Mind', the Start value should be ____ and the Number value should be ____.

Answering the Example

Use assignment: Quote ← 'Learning Never Exhausts The Mind'
Set Start ← 25, Number ← 8
OUTPUT SUBSTRING(Quote, Start, Number) displays 'The Mind'
OUTPUT LCASE(Quote) displays the string in lowercase.

What is the correct pseudocode to output the lowercase version of a string stored in Quote?

OUTPUT LCASE(Quote)
OUTPUT LOWERCASE(Quote)
OUTPUT TOLOWER(Quote)
OUTPUT LOWER(Quote)

What is a Trace Table?

A trace table is used to follow the values of variables as a program runs.
It helps you simulate code line by line and record outputs accurately.
Trace table questions are normally worth 3–6 marks and often involve iteration, selection, and arrays.

Which of these are true about trace tables?

Trace tables are used to follow variable values as a program runs.
Trace table questions are always worth 10 marks.
You may be asked to complete, explain, or spot errors in a trace table.
Trace tables only appear in Paper 2.

Command Words for Trace Table Questions

Complete: Fill in the table with correct values.
State: Give the value/output/result (usually a single word or number).
Explain: Say why something happens or changes in the program.
Identify: Spot where something goes wrong or doesn't match expectations.

If a trace table question says 'Identify', what should you do?

Fill in the table with correct values
Give a single word or number
Spot where something goes wrong
Say why something changes

Steps to Tackle a Trace Table Question

1. Read the code carefully – understand loops, IF statements, and variable changes.
2. Use the trace table provided – headings and row count guide the number of steps.
3. Work line by line – simulate the program and update variables after every change.
4. Watch out for variable resets – variables inside loops reset each iteration.
5. Show the final output clearly – write it exactly as it would appear on screen.

When tracing a loop, variables declared inside the loop often ____ every time the loop runs.

Worked Example: Trace Table

Algorithm: total ← 0, count ← 1, WHILE count ≤ 3, input number, IF number > 10 THEN total ← total + number, count ← count + 1, OUTPUT total.
Inputs: 12, 8, 15.
We need to complete the trace table with columns: Line number, count, number, total, Output.

After the first iteration of the loop (input 12), what are the values of count and total?

count = 1, total = 12
count = 2, total = 12
count = 2, total = 0
count = 1, total = 0

Completing the Trace Table

Step through each line: line 3 (WHILE), line 4 (INPUT), line 5 (IF), line 6 (total update), line 8 (count increment).
Use a new row for each variable change.
For lines that don't change variables (e.g., ENDIF, ENDWHILE), you can leave blank or use a dash.
Final output is 27 (12 + 15, since 8 is not >10).

In the trace table, when a column is not relevant, you should use a ____.

Which of these are good practices when completing a trace table?

Use a pencil and annotate each step.
Skip lines that don't change variables.
Keep your trace table neat.
Write the final output clearly.

Summary

For programming questions, use the five key questions to structure your answer.
For trace table questions, simulate code line by line and record variable changes.
Always read the code carefully and watch for variable resets in loops.
Present your final answer clearly, following CIE pseudocode notation.

Flashcards

What are the two papers in CIE IGCSE Computer Science that can contain programming questions?

Paper 1 and Paper 2. Paper 1 tests understanding and interpretation of algorithms; Paper 2 assesses designing, writing, testing, and refining programs.

What are the three acceptable formats for answering programming questions in CIE IGCSE Computer Science?

CIE pseudocode notation, Structured English, or a high-level programming language.

What five key questions should you ask yourself when writing a new program?

What are the inputs? What are the outputs? What processes take place? What constructs will I need to use? Do I need to use subprograms?

What does the SUBSTRING(Quote, Start, Number) function do?

It returns a string from Quote beginning at position Start that is Number characters long. The first character is at position 1.

What does LCASE(Quote) do?

It returns the lowercase version of the string Quote.

In the example, what pseudocode extracts and displays 'The Mind' from the string 'Learning Never Exhausts The Mind'?

Start ← 25, Number ← 8, OUTPUT SUBSTRING(Quote, Start, Number).

What is a trace table used for?

Trace tables are used to follow the values of variables as a program runs, testing your ability to simulate code line by line and accurately record outputs.

What command word means 'Fill in the table with correct values'?

Complete.

What command word means 'Give the value/output/result (usually a single word or number)'?

State.

What command word means 'Say why something happens or changes in the program'?

Explain.

What command word means 'Spot where something goes wrong or doesn't match expectations'?

Identify.

What are the five steps to tackle a trace table question?

1. Read the code carefully. 2. Use the trace table provided. 3. Work line by line. 4. Watch out for variable resets. 5. Show the final output clearly.

What is a common mistake when doing trace tables?

Skipping or misreading a line. Use a pencil and annotate each step.

In a trace table, when should you use a new row?

Whenever a variable or output changes.

What should you do if a column isn't relevant in a trace table?

Use a dash (–).

In the worked example, what is the output when inputs are 12, 8, 15?

27.

In the worked example, why is 8 not added to total?

Because 8 is not greater than 10, so the IF condition fails.

What does 'Watch out for variable resets' mean in trace tables?

Variables declared inside loops often reset every time; don’t carry the wrong value across iterations.

How many marks are trace table questions normally worth?

3–6 marks.

In which types of questions do trace tables most commonly appear?

Questions involving iteration, selection, and arrays/lists.

What is the fixed mark programming question at the end of Paper 2?

A 15-mark programming question.

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