28 processes P(1), ..., P(28) are concurrently executing on a system (see the pseudocode above with P(n)=P(28)). The shared variable called count is initialised to 2, while the semaphores s1, s2, ... , s(n-1), sn  are all initialised to 0.  What is the value of count when process P(13) executes semsignal(s12)?

Three processes A, B and C are admitted into the ready queue by the long-term scheduler. The processes are admitted -- first process C, then B, and then A -- without any delay between the admissions. The short-term scheduler uses a Round-Robin scheduling policy to assign processes to run on the CPU. The time quantum is  ns. The CPU burst times ns, ns and ns (for  A, B and C respectively) are all multiples of .  Assume , the processes make no I/O requests, and all of the processes successfully complete. You may also assume that no other processes or OS activity are important for your computations. 

Based only on the information given, which of the following formulae is the average wait time for these 3 processes? 

Hint: to deduce the correct average wait time, use 1) the correct formula for the average turnaround time from the last question, and 2) the relationship between turnaround times and wait times. 

Three processes A, B and C are admitted into the ready queue by the long-term scheduler. The processes are admitted -- first process C, then B, and then A -- without any delay between the admissions. The short-term scheduler uses a Round-Robin scheduling policy to assign processes to run on the CPU. The time quantum is ns. The CPU burst times ns, ns and ns (for  A, B and C respectively) are all multiples of . Assume , the processes make no I/O requests, and all of the processes successfully complete. You may also assume that no other processes or OS activity are important for your computations. 

Based only on the information given, which of the following formulae is the average turnaround time for these 3 processes? 

Hint: to deduce which of these formulae is correct, check which formula gives the same answer you got earlier for the average turnaround related to a C,B,A order of arrivals. 

Three processes A, B and C are admitted into the ready queue by the long-term scheduler. The processes are admitted -- first process C, then B, and then A -- without any delay between the admissions. The short-term scheduler uses a Round-Robin scheduling policy to assign processes to run on the CPU. The time quantum is 8ns. The CPU burst times are 104ns, 144ns and 192ns, for  A, B and C respectively. Assume that the processes make no I/O requests and all of them successfully complete. You may also assume that no other processes or OS activity are important for your computations. 

Based only on the information given, what is the average turnaround time (in ns) for these 3 processes? Give your answer to 2 decimal places.

A system with a First In First Out page replacement algorithm can store 3 pages in memory at any given time.

The diagram below illustrates the process, three time points have already been completed:

Complete the remaining pages with the incoming pages. Answer which pages are stored in the locations denoted "a?" and "b?". Write down your answer as a two digit response, e.g. if the pages were 8 and 9, write down 89 without spaces, commas or other symbols

Alice and Bob are exchanging information through a channel.  Alice and Bob speak a little known dialect of the Klingon family of languages.

Without their knowledge a third party is able to listen to their conversation, but this individual does not speak that dialect, does not record the conversation. However, the individual is able to transmit whilst they are exchanging information.

What problems could Alice and Bob be facing?

(select all that apply)

A system with a First In First Out page replacement algorithm can store 3 pages in memory at any given time.

The diagram below illustrates the process, three time points have already been completed:

Complete the remaining pages with the incoming pages. Answer which pages are stored in the locations denoted "a?" and "b?". Write down your answer as a two digit response, e.g. if the pages were 8 and 9, write down 89 without spaces, commas or other symbols

Alice and Bob are exchanging information through a channel.  Alice and Bob speak a little known dialect of the Klingon family of languages.

Without their knowledge a third party is able to listen to their conversation, but this individual does not speak that dialect and does not transmit whilst they are exchanging information. However, the individual is able to record the conversation.

What problems could Alice and Bob be facing?

(select all that apply)

A system with a First In First Out page replacement algorithm can store 3 pages in memory at any given time.

The diagram below illustrates the process, three time points have already been completed:

Complete the remaining pages with the incoming pages. Answer which pages are stored in the locations denoted "a?" and "b?". Write down your answer as a two digit response, e.g. if the pages were 8 and 9, write down 89 without spaces, commas or other symbols

Consider a

swapping system that has a series of holes (all in MB) with the following sizes (in order):

10,  4,  11,  18,  7,  9,  13,  15 

Three processes of sizes  14, 12, 3 MB arrive in order.  Select the correct order of the holes selected if a  best fit strategy is used.