Abstract: A computer file system, in which directory files and real files are organized in a tree structure, includes data items which are recorded in a high-ranking directory file in the tree structure, a high-ranking file management table which records file management data indicative of the assignment relation with low-ranking directory files or real files created below the high-ranking directory file, and a low-ranking file management data which is stored in any of the low-ranking directory files and indicative of the assignment relation between the low-ranking directory file and other low-ranking directory files or real files. The system further includes an assignment relation copy device which copies the file management data of a high-ranking or low-ranking file management table indicative of the assignment relation between the high-ranking or low-ranking directory files or real files into another high-ranking or low-ranking file management table.

Abstract: A virtual machine system has a processor operating as a base machine which includes a plurality of groups of registers, such as data registers, address registers and instruction address registers which are selected according to identification data identifying individual virtual machines. A respective group of registers is allotted to each virtual machine and to the virtual machine monitor in the system. A status register file is provided to effect selective access to a respective one of a plurality of status registers in the system in accordance with a virtual machine number. An interrupt processing portion is provided comparing the value of an interrupt mask level of the status word of a corresponding virtual machine with an externally generated interrupt level to control interrupt processing.