How to Answer Trace Table Questions (Cambridge (CIE) IGCSE Computer Science): Revision Note

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

This algorithm inputs three numbers and calculates the total if they are greater than 10:

01 total ← 0  
02 count ← 1  
03 WHILE count ≤ 3  
04     number ← INPUT  
05     IF number > 10 THEN  
06         total ← total + number  
07     ENDIF  
08     count ← count + 1  
09 ENDWHILE  
10 OUTPUT total  

Complete the trace table below when the inputs are: 12, 8, 15

You may not need to use all the rows in the table

1. Read the code carefully

• Line 1: Sets total to 0

• Line 2: Sets count to 1

• Lines 3–9: Loop runs 3 times (count from 1 to 3)

  • Each time, a number is input

  • If it’s greater than 10, it’s added to total

  • Then count increases by 1

• Line 10: Outputs the final total after the loop finishes

2. Use the trace table provided

• The trace table includes 15 rows, one for each step where a variable changes

• You should use a new row whenever a variable or output changes

• If you only use 5–6 rows, something’s probably missing

3. Work line by line

03 WHILE count ≤ 3

count = 1 → loop runs

04 number ← INPUT

User inputs 12

05 IF number > 10 THEN

12 > 10 → go to line 6

06 total ← total + number

total becomes 12

08 count ← count + 1

count becomes 2

03 WHILE count ≤ 3

count = 2 → loop runs

4. Watch out for variable resets

• number changes each time new input is entered

• total only changes if the input is greater than 10

• count increases on every loop

• There are no nested loops, so trace line by line in order

5. Show the final output clearly

10 OUTPUT total

The output is 27

Final answer