Abstract: A data processing system operates in a multiprogramming mode in which a plurality of different tasks are performed, at least one of the tasks being interruptable by another one of the tasks, and the system includes at least one facility which is not used by all of the tasks. The method of operating the system includes the steps of permitting access to the facility by a first task requesting such access, detecting the interruption by a second task of the first task prior to completion of the first task's use of the facility, and preventing access to the facility by any task until the data and state information in the facility relative to the first task has been stored outside the facility.

Abstract: A memory management system method increases the size of a segment in blocks of 64K virtual pages in response to the system detecting that the requested page has been protected. The conventional UNIX type System Calls create and open files in virtual memory. All pages are protected "read only" until a SHMAT type System Call is made to operate on a page at a specific address. At that point in the process, a protection exception is recognized by the system and the UNIX kernel takes control to remove the protection and update the appropriate data structures to reflect the new status of the page and the addresses in real memory where the page may be found. Segments containing mapped files are also extended by the method.