Software updating method and portable terminal device

摘要

A software updating method for updating software stored as compressed code in a nonvolatile memory provided in a portable terminal on the basis of differential data via wireless communication includes the steps of providing a file system area having a fault-tolerant property; decompressing, at the execution of software updating, the compressed code of the software and loading the decompressed code into a random-access memory; updating the software in the random-access memory on the basis of the differential data; compressing the updated software; and storing a backup of a compressed updated code sequence corresponding to a compressed updated portion of the compressed updated software in the file system area and then writing the compressed updated code sequence corresponding to the compressed updated portion of the compressed updated software back to the nonvolatile memory.