Safety in computer systems is a measurement of the system’s ability to avoid unwanted harm, loss, injury, or damage. Safety is of significant concern when the systems’ use involves a hazard (the likelihood of injury, damage, loss, or death if the system is operated in an unsafe manner), and is a fundamental characteristic of safety-critical systems. Safety is one of four aspects of system dependability; the other three are availability, reliability, and security.
A safe system is not necessarily highly available; systems can degrade system performance to the point that irresponsible operators may attempt to disable them. In addition, a safe system is not necessarily reliable; in radiation therapy, concerns warrant that the device should shut down rather than administer potential lethal radiation doses. See availability, hazard, reliability, safety-critical system, security.