Thư viện tài liệu, ebook tham khảo dành cho học sinh, sinh viên

Examples include Windows, Linux  familiar interfaces facilitate portability  slower and less predictable than special purpose embedded OS  not optimized for real-time and embedded applications  require considerable modification to achieve adequate performance optimizes for the average case rather than the worst case for scheduling assigns ...

16 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1692 | Lượt tải: 0

A wide variety of access rights have been used by various systems often as a hierarchy, with each right implying those that precede it. None User may not know the existence of file by not allowing to read the user directory that includes this file Knowledge User can only determine that the file exists and who its owner is

42 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1217 | Lượt tải: 0

SCAN is biased against the area most recently traversed  does not exploit locality SCAN favors jobs whose requests are for tracks nearest to both innermost and outermost tracks and the latest-arriving jobs

45 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 988 | Lượt tải: 0

 Predictability of longer processes is reduced.  Need to know or estimate the required processing time for each process. Programmers may be required to supply an estimate for batch jobs. Statistics may be gathered for repeating jobs. If estimated processing time is not correct, OS may abort it.

48 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1702 | Lượt tải: 0

Determines where in real memory a process piece is to reside Important in a segmentation system such as best-fit, first-fit, and etc are possible alternatives Irrelevant for pure paging or combined paging with segmentation

51 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1151 | Lượt tải: 0

Next-fit Scans memory from the location of the last placement  More often allocate a free block at the end of memory where the largest block is found The largest block of free memory is quickly broken up into smaller blocks Compaction is required more frequently

43 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1006 | Lượt tải: 0

When a process makes a request for a set of resources, assume that the request is granted, update the system state accordingly, Then determine if the result is a safe state. if so, grant the request and, if not, block the process until it is safe to grant the request.

54 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1127 | Lượt tải: 0

A data area (e.g., a file) is shared among many processes Some processes (readers) only read the data area, some (writers) only write to the area Conditions to satisfy: Multiple readers may simultaneously read the file Only one writer at a time may write If a writer is writing to the file, no reader may read it

42 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1099 | Lượt tải: 0

Like processes, thread may synchronize with one another. Any alteration of a resource by one thread affects other threads in the same process consider two threads each try to add an element to a linked list at the same time

20 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 1098 | Lượt tải: 0

What is a process? Process states which characterize the behaviour of processes. Data structures used to manage processes. Ways in which the OS uses these data structures to control process execution.

56 trang | Chia sẻ: huyhoang44 | Ngày: 17/03/2020 | Lượt xem: 941 | Lượt tải: 0