What is defensive programming?

• A. Designing a device so that it keeps working even if errors occur
• B. Optimizing code for speed
• C. Writing code for attack surfaces
• D. Designing a program that refuses to handle errors

Answer: (A)

Defensive programming is about making software resilient to errors and unexpected conditions. The goal is to anticipate possible misuses, invalid inputs, or unforeseen states and code in a way that the system continues to function, or at least fails in a safe, controlled manner, rather than crashing or producing corrupt results. This often includes validating inputs, checking boundaries, handling exceptions gracefully, cleaning up resources, and providing clear error reporting so the program can recover or degrade gracefully when something goes wrong. The idea is to design for reliability and safety, so the software keeps operating even in the face of problems.

So, the best match is designing a system that keeps working or fails safely when errors occur, rather than optimizing for speed, focusing on attack surfaces, or refusing to handle errors.