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Operating systems exams - multiple choice questions (MCQ) and answers, Objective type questions
Operating
Systems MCQ questions and answers – Set 19
1. The text segment of a process address
space contains:
(a) The statically
allocated data associated with the process
(b) The dynamically
allocated data associated with the process
(c) The executable code
associated with the process
(d) The inter-process
communication (IPC) messages for the process
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Ans : (c)
Answer: (c) The
executable code associated with the process
A
process has at least three segments of usable addresses:
- A
text segment contains the executable image of the program. Another text
segment is created for each dynamic shared object (DSO) with which a process
is linked.Text segments are always read-only.
- A
data segment contains the “heap” of dynamically allocated data space. A
process can create additional data segments in various ways described later.
- A
stack segment contains the function-call stack. This segment is extended
automatically as needed.
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2. Large page sizes increase ______
(a) Internal fragmentation
(b) External fragmentation
(c) The page table size
(d) The working set size
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Ans : (a)
Answer: (a) Internal
fragmentation
Internal
fragmentation: unused memory within an allocation unit
External
fragmentation: unused memory outside allocation units
Large
page size: increases chance that we get more memory than we need. Larger page
sizes lead to large amount of wasted memory, as more potentially unused
portions of memory are loaded into main memory.
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3. What is the advantage of a multilevel
(hierarchical) page table over a single-level one?
(a)
Page number lookups are faster
(b) The page table can
consume much less space if there are large regions of unused memory.
(c) Each segment (code,
data, stack) can be managed separately.
(d) Page permissions can
be assigned at a finer granularity.
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Ans : (b)
Answer: (b) The page
table can consume much less space if there are large regions of unused memory
Any
regions of memory that are not mapped for a region covered by a top-level
page number do not need to have a lower-level page table allocated. This
avoids the need to allocate the lower-level page table for that region.
Multi-level
paging
Multi-level
page table is a paging scheme that consists of two or more levels of page
tables in a hierarchical manner. In this scheme, a virtual address is divided
into three or more sections, with all but the last section being page numbers
in different page tables, and the last one being the offset.
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4. What each partition may contain when
memory is divided into several fixed sized partitions?
(a) Exactly one process
(b) At least one process
(c) Multiple processes
(d) None of these
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Ans : (a)
Answer: (a) Exactly one
process
One
of the simplest methods for memory allocation is to divide memory into
several fixed-sized partitions. Each partition
may contain exactly one process. In this multiple-partition method,
when a partition is free, a process is selected from the input queue and is
loaded into the free partition. When the process terminates, the partition
becomes available for another process. The operating system keeps a table
indicating which parts of memory are available and which are occupied.
Finally, when a process arrives and needs memory, a memory section large
enough for this process is provided.
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5. What will happen if the memory
allocated to a process is slightly larger than the process?
(a) External fragmentation
occurs
(b) Internal fragmentation
occurs
(c) Both (a) and (b)
(d) Neither (a) nor (b)
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Ans : (b)
Answer: (b) Internal
fragmentation occurs
Due
to the rules governing memory allocation, more computer memory is sometimes
allocated than is needed. For example, memory can only be provided to
programs in chunks (multiple of 4), and as a result if a program requests
perhaps 29 bytes, it will actually get a chunk of 32 bytes. When this
happens, the excess memory goes to waste. In this scenario, the unusable
memory is contained within an allocated region. This arrangement, termed
fixed partitions, suffers from inefficient memory use - any process, no matter
how small, occupies an entire partition. This waste is called internal
fragmentation. [Wikipedia]
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