Top 10 Mistakes Students Make in GCSE Computer Science Programming Exams

IntroductionEvery year, GCSE Computer Science examiners’ reports highlight common mistakes students make. The good news is that most of them are avoidable. Here are the 10 errors I see most often when tutoring, and how you can avoid them.

1. Indentation Errors

Python requires consistent indentation. Forgetting one space can break the code.

2. Incorrect Use of Variables

Reusing variable names or mixing strings with integers.

3. Confusing = and ==

= assigns a value, == checks equality.

4. Off-by-One Errors in Loops

Using range(0, len(list)) instead of range(len(list)).

5. Forgetting to Close Loops/If Statements

Missing colons or misaligned blocks.

6. Ignoring Data Types

e.g., adding a string to an integer.

7. Weak Input Validation

Not checking user inputs, leading to crashes.

8. Forgetting Edge Cases

Empty lists, zero values, or boundary numbers.

9. Misunderstanding Boolean Logic

Mixing up and vs or.

10. Not Reading the Question Carefully

Writing code that works, but not what the exam asked.

Input Validation Fix

age = input("Enter your age: ")
if age.isdigit():
    age = int(age)
    print("You are", age, "years old.")
else:
    print("Please enter a number!")

Conclusion

By practising past questions, reviewing common pitfalls, and working with a tutor, you can avoid these mistakes and secure more marks.