운영체제2장(xpupdate)

목차

2.1 Prefetching is a method of overlapping the I/O of a jaob with the job`s own computation. The idea is simple. After a read operation completes and the jop is about to start operation on the data, the input device is instructed to begin the next read immediately. The CPU and input device are then both busy. With luck, by the time that the job is ready for the next data item, the input device will have finished reading that data item. The CPU can then begin processing the newly read data, while the input device starts to read the following data. A similar idea can be used for output. In this case, the job creates data that are put into a buffer until an output device can accept them.
Compare the prefetching scheme with sppling, where the CPU overlaps the input of one job with the computation and output of other jobs.

2.3 What are the differences between a trap and an interrup? What is the use of each function?

2.5 Which of the following instructions should be privileged?

2.7 Some early computers protected the operationg system by placing it in a memory partition that could not be modified by either the user job or the operationg system itself. Describe two difficulties that you think could arise with such a scheme.

2.9 Give two reasons why caches are useful.

2.11 Some CPUs provide for more than two modes of operation. What are two possible uses of these multiple modes?

본문내용

2.3 What are the differences between a trap and an interrup? What is the use of each function?
정답 : 트랩 - 오류(예를 들어, 0으로 나누기 또는 부적절한 기억장치 접근), 혹은 사용자 프로그램이 운영체제 서비스를 요청하는 소프트웨어 방식의 인터럽트이다.
실행중인 프로그램 내에 테스트를 위해 특별한 조건을 걸어 놓은것.
예를 들어, ‘인터럽트를 트랩한다’ 는 것은 특정한 인터럽트가 발생할 때까지 기다렸다가 그에 해당하는 루틴을 실행 하는 것을 말한다. 에러 트랩은 에러 조건을 시험하고, 복원 루틴을 제공하기 위한 것이다. 디버깅 트랩은 특정 명령어의 실행을 기다렸다가 그 프로그램을 중지시키고, 바로 그 순간의 시스템 상태를 분석한다.
인터럽트 - 현재 하던 작업을 멈추고 요구된 작업을 수행한 다음 원래 하던 작업을 계속하는 처리 방식.

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