Abstract: A method and system have a feature of rewriting an application program to a nonvolatile rewritable memory in a way that allows for prevention of execution or corrupted program or recovery from failures that occur during execution of the application program. Before writing the application program to a first segment of the memory, an indicator is written to a second segment of the memory, indicating that the first segment of memory contains "invalid" information. At least the first segment, but not the second segment, is then erased and the application program is then written to the first segment. If the writing process is not completed, perhaps due to an unforseen disturbance (e.g., power outage) in the system, the first segment retains the indicator without changing the indicator's value. However, if the writing process is completed, a control processor determines that the writing process is completed and changes the indicator in the first segment to a value indicative of "valid" data.