Operating systems MCQ questions set 4 for competitive exams with answers explained
Operating systems MCQ Set - 4
1.
Consider a disk with the following characteristics; Find the size of each sector of the given disk.
• Number
of surfaces: 8 (= 23)
• Number
of tracks / surface: 512 K (= 219)
• Number
of bytes / track: 8 MB (= 223 bytes)
• Number
of sectors / track: 8 K (= 213)
• On-disk
cache: 16 MB (= 224 bytes)
a.
1 KB
b.
2 KB
c. 4 KB
d. 8 KB
Answer:
Sector capacity =
No. of bytes per track * no. of tracks per sector
= 223 *
1/213 = 223/213 = 210
bytes/sector
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2.
Suppose you had a computer that supported virtual memory and had 32-bit virtual
addresses and 4KB (212 byte) pages. If a process actually uses 1024
(210) pages of its virtual address space, how much space would be
occupied by the page table for that process if a single-level page table was
used? Assume each page table entry occupies 4 bytes.
a. 2 MB
b. 4 MB
c. 8 MB
d. None of the above
Answer:
Number of pages
in the address space = 232/212 = 220 pages.
Therefore, a
single level page table would have 220 entries, where each entry
is 4 bytes. Therefore,
Space required by
the page table = 4 * 220 bytes = 4 MB.
This is
independent of how many pages are actually being used.
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3.
A CPU burst is
a. an example of priority
inversion where a low priority process gets access to the CPU.
b. a temporary increase in
the priority of a process to ensure that it gets the CPU.
c. an unexpected increase
in a process' need for computation.
d. the period of time that a process uses the processor between
I/O requests.
Answer:
A CPU burst is
the period of time that a process is executing instructions before it gets to
a waiting state on
some event (usually I/O but also things like messages or semaphores).
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4.
Compared to a non-preemptive scheduler, a preemptive scheduler can move processes
from the:
a. running to the blocked state.
b. ready to the running state.
c. blocked to the ready state.
d. running to
the ready state.
Answer:
A preemptive
scheduler can stop a process from running and have
another process run.
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5.
The main advantage of DMA is that it
a. Increases the speed of
the CPU
b. Increases the speed of
the data bus
c. Increases the performance of the system by allowing more
things to happen at once
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