Operating Systems Questions (Please help if you can)

1. What is the similarity between multiprogramming and time-sharing? What are the

differences between the two?

2. When a process is terminated, it enters a state called exit. In this state, all the

resources allocated to the process are reclaimed by the os. Yet, the process may remain in

exit state for an extended period of time. Why is this so even when the process has no

memory allocated to it?

3. Consider two processes p1 and p2 that are scheduled by the kernel K. Indicate which

out of the three actors p1, p2, and K causes the following state changes:

(a) Transition of p1 from ready to running.

(b) Transition of p1 from running to blocked.

(c) Transition of p1 from running to ready.

(d) Transition of p1 from blocked to ready.

4. A computer has cache, main memory, and a disk used for virtual memory. If a

referenced word is in the cache, 20ns are required to access it. If it is in main memory but not

in the cache, 60ns are required to load it into the cache (this includes the time to originally

check the cache), and then, the reference is started again. If the word is not in main memory,

12ms are required to fetch the word from disk, followed by 60ns to copy it to the cache, and

then, the reference is started again. The cache hit ratio is 0.9 and the main memory hit ratio

is 0.6. What is the average time in ns required to access a referenced word on this system?