Abstract: A duplex data system performs a recovery process normally even in the event of an abrupt abnormal power failure. The duplex data system has a first storage device, a second storage device, and a control unit for duplicating data by storing the data in the first storage device and the second storage device. For duplicating the data, the control unit first writes the data into the first storage device and, after having completed the writing of the data into the first storage device, writes the data into the second storage device.

Abstract: A duplex data system performs a recovery process normally even in the event of an abrupt abnormal power failure. The duplex data system has a first storage device, a second storage device, and a control unit for duplicating data by storing the data in the first storage device and the second storage device. For duplicating the data, the control unit first writes the data into the first storage device and, after having completed the writing of the data into the first storage device, writes the data into the second storage device.

Abstract: A computer apparatus comprises a read-only memory, a non-volatile memory, a random access memory and a controller. The read-only memory is a memory in which a program composed of a plurality of modules each have a particular function is written. The non-volatile memory is a writable memory which stores a replacing module which is formed by correcting an error within a defective module of the program. The random access memory is readable and writable. The controller transfers the replacing module from the non-volatile memory into the random access memory, executes the program written in the read-only memory, reads and executes the replacing module stored in the random access memory, instead of reading the defective module.

Abstract: Disclosed is a method far backing up memory and calendar, which has the steps of: providing a back-up power source for the calendar separated from the back-up power source for both the memory and the calendar; and continuing to back up the calendar by the separated back-up power source even after stopping the backing-up of the memory. Also disclosed is a circuit for backing up memory and calendar, which has a first power source circuit to supply back-up current to both the memory and the calendar; and a second power source circuit to supply continuously back-up current to the calendar when the supply of back-up current to the memory stops due to reduction in the capacity of the first power source circuit.

Abstract: A data back-up system of the present invention is applicable to a portable data terminal and includes an exclusive read/write controller for exclusively controlling the writing and reading of data out of a first nonvolatile memory. Only the control over the entire data terminal is assigned to a main controller. A volatile memory serves as a work area while a second nonvolatile memory stores system software including an operating system. The exclusive read/write controller makes it needless for the main controller to wait until all the necessary data have been written to the first nonvolatile memory. Moreover, the system implements rapid and reliable data back-up without resorting to a battery.