Abstract: A computer having both volatile and nonvolatile memory, and which is operative in response to a system program and an application program, is protected against an interruption of a primary power source by a momentary introduction of power from a backup source, and by a freezing of data and program instructions in effect at the time of the power interruption. A backup region is designated within the nonvolatile storage medium for receipt of data and instructions present in the nonvolatile memory upon the occurrence of a power interruption. Circuitry is provided for sensing the interruption, the circuitry including the implementation of a computer program which directs cessation of further operation of the application program followed by a transfer of data and instructions from the volatile memory to the nonvolatile memory. This transfer is done under backup power. Thereupon, the backup power is discontinued and the computer is shut down.