Saving the current state of a program and its data, including intermediate results to disk or other non-volatile storage, so that if interrupted the program could be restarted at the point at which the last checkpoint occurred. This facility came into popular use in mainframe operating systemss such as OS/360 in which programs frequently ran for longer than the mean time between system failures. If a program run fails because of some event beyond the program's control (e.g. hardware or operating system failure) then the processor time invested before the checkpoint will not have been wasted.