Operating systems MCQ questions set 5 for competitive exams with answers explained
Operating systems MCQ Set - 5
1. Which of the following C library functions do NOT directly
correspond to (similarly named) system calls? That is, the implementations of
which of these C library functions are NOT straightforward invocations of the
underlying system call?
a. system()
b. fork()
c. exit()
d. strlen()
Answer: both (a) and (d)
system and strlen
are both C functions used to execute a bash shell command and to return the length
of a string respectively. On the other hand, both fork and exit are system
calls used to create a new child process and to terminate the current process
respectively.
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2. Which of the following are all system calls?
a. chmod(), chdir(),
read(), main()
b. waitpid(), smdir(),
mount(), open()
c. fork(), exit(), lseek(), kill()
3. A round robin scheduler:
a. favors processes that
are expected to have a short CPU burst.
b. favors high priority
processes.
c. dynamically adjusts the
priority of processes based on their past CPU usage.
d. gives each process an equal share of the CPU.
Answer: (d)
A round robin
scheduler is basically first-come, first-served with preemption: a process
can run until it blocks or until its time slice expires. Then it’s put at the
end of the queue and every other process that’s ready to run gets to run. No
estimation of CPU burst, no priorities.
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4. A shortest remaining time first scheduler:
a. dynamically adjusts the
quantum based on the process.
b. tries to optimize mean response time for processes.
c. gives each process an
equal share of the CPU.
d. favors processes that
use the CPU for long stretches of time.
Answer: (b)
A SRTF scheduler
tries to estimate the next CPU burst of each process by weighing past CPU bursts.
It then sorts processes based on this estimated burst time. This causes
short-cpu-burst processes to be scheduled first and optimizes the average
response time.
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5. Process aging:
a. helps estimate the
length of the next compute period.
b. increases the runtime
of a process.
c. improves the chances of a process getting scheduled to run.
d. is a count of the total
CPU time used by the process and is stored in the PCB.
Answer: (c)
Process aging is
when you temporarily increase the priority of a low-priority process that has
not been run in a while to ensure that it gets a chance to get scheduled to
run.
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