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2. In a uniprocessor system, processes A, B, C arrive at the system at the same time in

that order, each process has a series of alternating CPU bursts and 1/0 bursts as

follows:

A: Sms (CPU), 7ms (1/0), 6ms (CPU)

B: 2ms (CPU), 1ms (1/0), 3ms (CPU), 1ms (1/0), 1ms (CPU)

C: Sms (CPU), 3ms (1/0), 4ms (CPU)

What would be the turnaround (completion) and wait times of all processes using

each of the following scheduling algorithms?

Round Robin (RR) with 3ms time quantum,

Shortest Job First (SJF).

For simplicity, assume context switch time and other overheads are comparatively

negligible. NOTE:

• During the CPU burst (execution) of a process, I/O bursts of other processes

would be happening at the same time.

• Wait time is the wait time each process spends in the process READY queue.

• Turnaround time-CPU bursts + I/O bursts + Wait time

Fill in the following table with your answers, and you must show the steps of your

calculation (follow the hints below).

Turnaround Time

A

c

C

Average

RR

SJF

Wait Time

RR

SJF

Hint: Use notation p (e, s. r) to track CPU execution of a process over the time:

e-total CPU burst time that has been executed for a particular process,

s-total system time passed from the beginning of executing first process,

r-the reason why the process is stopped along the execution (either

suspended or completed) due to:

• t-time quantum expired during RR (only applicable to RR),

• I-process initiated an I/O,

• c-process completed execution

. For example: A(10, 16, t) means total CPU burst time that has been

executed for process A is 10ms, total system time passed is 16ms

since the beginning of executing the first CPU burst, and process A is

suspended due to expiration of time quantum.

Fig: 1