Which of the following is an example of spooled device?

Four jobs to be executed on a single processor system arrive at time $${0^ + }$$ in the order $$A, B, C, D.$$ their burst $$CPU$$ time requirements are $$4, 1, 8, 1$$ time units respectively. The completion time of A under round robin scheduling with time slice of one time units.

A critical section is a program segment

The concurrent programming constructs fork and join are as below: Fork (label) which creates a new process executing from the specified label join (variable) which decrements the specified synchronization variable (by 1) and terminates the process if the new value is not 0. Show the precedence graph for S1, S2, S3, S4 and S5 of the concurrent program below.
N = 2
M = 2
fork L3
fork L4
S1
L1 : join N
S3
L2: join M
S5
L3:S2
goto L1
L4:S4
goto L2
next: