Code Sheets, Exam Technique & Mistakes: Common Examiner-Reported Mistakes In Paper 2 (Copy)
Common Examiner-Reported Mistakes In Paper 2 (Cambridge Standard – O Level 2210 + IGCSE 0478)
Why Examiner-Reported Mistakes Are The Fastest Way To Improve Scores
- Examiner reports are written after:
- Reviewing thousands of scripts
- Mistakes listed are:
- Repeated
- Predictable
- Preventable
- Most Paper 2 marks are lost:
- Not due to lack of knowledge
- But due to avoidable technique errors
- Understanding these mistakes:
- Gives instant score improvement
- Without learning new content
Category 1: Writing Programming Code Instead Of Pseudocode
What Examiners Report
- “Many candidates wrote solutions in a specific programming language”
- “Use of Python / C / Java syntax was penalised”
Common Mistakes
- Using:
print()input()i++=={ }
- Writing:
for(i=0; i<n; i++)
Why Marks Are Lost
- Mark schemes are based on:
- Cambridge pseudocode
- Language-specific syntax:
- Cannot be matched reliably
Examiner Advice (Implied)
- Use:
- INPUT
- OUTPUT
- IF / ENDIF
- WHILE / ENDWHILE
- FOR / ENDFOR
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Category 2: Incorrect Or Missing Loop Termination Conditions
What Examiners Report
- “Loops frequently ran beyond intended limits”
- “Termination conditions were omitted or incorrect”
Common Mistakes
- Forgetting:
- index increment
- Using:
- OR instead of AND
- Missing:
- Boundary checks
- Infinite loops caused by:
- Flags never updated
Typical Example
Incorrect:
- WHILE found = FALSE DO
Correct:
- WHILE index <= n AND found = FALSE DO
Why This Loses Marks
- Infinite loop risk
- Unsafe algorithm
- Logical correctness compromised
Category 3: Confusing WHILE And REPEAT UNTIL Logic
What Examiners Report
- “Many candidates treated REPEAT UNTIL as a WHILE loop”
Common Mistakes
- Using:
- UNTIL condition that should be FALSE
- Expecting:
- REPEAT UNTIL to stop when condition is FALSE
- Writing:
- Condition logic backwards
Correct Mental Model
- WHILE:
- Continues while condition is TRUE
- REPEAT UNTIL:
- Stops when condition is TRUE
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Category 4: Incorrect Boolean Logic (AND / OR / NOT)
What Examiners Report
- “Boolean conditions were often logically incorrect despite correct syntax”
Common Mistakes
- Using OR instead of AND in:
- Range checks
- Misplacing NOT
- Missing brackets in compound conditions
Example Error
Incorrect:
- IF x >= 0 OR x <= 100 THEN
Correct:
- IF x >= 0 AND x <= 100 THEN
Impact
- Conditions become:
- Always TRUE
- Or always FALSE
- Decision logic fails completely
Category 5: Not Following Pre-Release Context Properly
What Examiners Report
- “Some candidates ignored details provided in the pre-release material”
Common Mistakes
- Assuming:
- Different input ranges
- Different data structures
- Renaming variables inconsistently
- Ignoring stated constraints
Examiner Expectation
- Use:
- Same variable names
- Same logic assumptions
- Same data meaning
- Pre-release is:
- Binding context, not optional reading
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Category 6: Poor Trace Tables And Unclear Working
What Examiners Report
- “Trace tables were often unclear or incomplete”
- “Values were written without clear association to variables”
Common Mistakes
- Missing:
- Column headings
- Mixing:
- Variable values
- Skipping:
- Iterations
- Writing:
- Only final output
Result
- Method marks cannot be awarded
- Examiner cannot follow logic
Category 7: Writing Too Much Or Too Little
What Examiners Report
- “Some candidates wrote unnecessarily complex solutions”
- “Others provided insufficient detail”
Overwriting Mistakes
- Adding:
- Extra loops
- Extra conditions
- Unasked features
Underwriting Mistakes
- Writing:
- Only final output
- One-line answers for multi-step questions
Examiner Preference
- Exactly what the question asks
- No more, no less
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Category 8: Incorrect Use Of Procedures And Functions
What Examiners Report
- “Procedures and functions were frequently confused”
Common Mistakes
- Returning values from procedures
- Forgetting RETURN in functions
- Using CALL with functions
- Passing parameters incorrectly
Correct Distinction
- Procedure:
- Performs task
- Does not return value
- Function:
- Returns a value
- Used in expressions
Category 9: Inconsistent Or Unsafe Array Indexing
What Examiners Report
- “Array indices were frequently out of bounds”
Common Mistakes
- Starting at index 0 without declaration
- Looping beyond array size
- Not protecting index in WHILE loops
Examiner Expectation
- Clear DECLARE statement
- Safe loop boundaries
- Index consistency
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Category 10: Poor Layout And Illegible Structure
What Examiners Report
- “In some scripts, it was difficult to follow the logic due to poor presentation”
Common Issues
- No indentation
- Crowded writing
- Overwriting corrections
- Outputs mixed with calculations
Consequence
- Examiner cannot confidently award marks
- Correct logic may receive partial credit only
Category 11: Ignoring Command Words
What Examiners Report
- “Some candidates did not respond appropriately to the command word”
Examples
- Asked to:
- “State the output”
- Candidate:
- Explains logic instead
- Asked to:
- “Write pseudocode”
- Candidate:
- Draws flowchart
Examiner Rule
- Marks are awarded only for:
- What the command word requests
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Category 12: Not Continuing After Making A Mistake
What Examiners Report
- “Some candidates abandoned questions after an early error”
Reality
- Cambridge applies:
- Error-carried-forward (ECF)
- One mistake:
- Does not zero the question
Correct Strategy
- Continue tracing
- Continue updating variables
- Continue writing outputs
Category 13: Guessing Instead Of Tracing
What Examiners Report
- “Final answers were given with no supporting working”
Impact
- Guessing = zero marks if wrong
- Tracing = partial marks even if wrong
Category 14: Misinterpreting Output Requirements
What Examiners Report
- “Some candidates wrote commentary instead of values”
Common Mistakes
- Writing:
- “The output will be 10”
- Instead of:
- 10
Examiner Expectation
- Output values only
- Correct order
- Correct format
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Computer Science Full Scale Course
Final Examiner-Warning Checklist (Memorise)
- Use Cambridge pseudocode only
- Terminate loops safely
- Apply Boolean logic carefully
- Respect pre-release context
- Show tracing clearly
- Answer exactly what is asked
- Keep layout clean
- Continue after mistakes
Final Lock-In Rules
- Most Paper 2 mistakes are technique-based
- Examiner reports repeat the same warnings yearly
- Avoiding these errors boosts grades immediately
- Clean logic + clean presentation = maximum marks