Abstract: A method of operating a computing device having NAND flash memory for storage of program code and user data. At start up, only selected components of the computing device core operating system are shadowed into RAM. Other components, such as read only system files associated with the core operating system, are retained in the NAND flash memory and only shadowed into RAM upon demand. The program codes shadowed into RAM at start up and the program codes shadowed into RAM upon demand are presented to a file server of the computing device as a composite file system. The use of the composite file system reduces the amount of RAM permanently occupied by core operating system code during operation of the device and also enhances the use of the more power efficient NAND flash memory. Moreover, the boot up time of the device is also significantly reduced.

Abstract: A mobile wireless device programmed with a file system which is partitioned into multiple root directories. The partitioning of the file system ‘cages’ processes as it prevents them from seeing any files they should not have access to. A Trusted Computing Base verifies whether or not a process has the required privileges or capabilities to access root sub-trees. The particular directory a file is placed into automatically determines its accessibility to different processes—i.e. a process can only access files in certain root directories.

Abstract: A method of operating a computing device having NAND flash memory for storage of program code and user data. At start up, only selected components of the computing device core operating system are shadowed into RAM. Other components, such as read only system files associated with the core operating system, are retained in the NAND flash memory and only shadowed into RAM upon demand. The program codes shadowed into RAM at start up and the program codes shadowed into RAM upon demand are presented to a file server of the computing device as a composite file system. The use of the composite file system reduces the amount of RAM permanently occupied by core operating system code during operation of the device and also enhances the use of the more power efficient NAND flash memory. Moreover, the boot up time of the device is also significantly reduced.

Abstract: A mobile wireless device programmed with a file system which is partitioned into multiple root directories. The partitioning of the file system ‘cages’ processes as it prevents them from seeing any files they should not have access to. A Trusted Computing Base verifies whether or not a process has the required privileges or capabilities to access root sub-trees. The particular directory a file is placed into automatically determines its accessibility to different processes—i.e. a process can only access files in certain root directories. This is a light weight approach since there is no need for a process to interrogate an access control list associated with a file to determine its access rights over the file—the location of the file taken in conjunction with the access capabilities of a process intrinsically define the accessibility of the file to the process.