A programmer uses defensive design when writing a program.

Mark scheme

Marking points from the official mark scheme. The mark or mark type is shown in brackets.

1. 6(a) Up to two of: B1 for each point.
2. (To prevent unexpected inputs from causing the program to crash / behave unexpectedly / become corrupted) (1)
3. (To prevent malicious inputs from causing security vulnerabilities) (1)
4. (To make the program robust / reliable / secure / error-free) (1)
5. 6(b)(i) Up to two of: B1 for each point.
6. Checking data / input (1)
7. To ensure it is sensible / reasonable / meets requirements / valid (1)
8. 6(b)(ii) Up to two of: B1 for naming a check, B1 for describing.
9. Example: Length check / type check / range check / presence check / format check (1)
10. Description: (1) E.g. Length check ensures string / data has minimum / maximum number of characters. / Type check ensures data is of specific type (e.g. integer, string, Boolean). / Range check ensures data is within specific range (e.g. 1-100). / Presence check ensures data is not empty / null. / Format check ensures data is in specific format (e.g. email address, postcode, date).