In the context of computer software, robustness is the resilience of the system, especially when under stress or when confronted with invalid input. For example, an operating system is considered robust if it operates correctly when it is starved of memory or storage space, or when confronted with an application that has bugs or is behaving in an illegal fashion - such as trying to access memory or storage belonging to other tasks in a multitasking system.

Most modern computer designs have memory protection hardware allowing processes to be forcibly confined to their own memory space. In older designs, such as most 8-bit systems and many early 16-bit ones, this was not available, and thus system integrity was preserved mainly by clean design and careful coding. Thus the perceived robustness of a system became a major factor in debates about different machines and operating systems' quality and performance.