Operating systems TRUE / FALSE questions for competitive exams
Operating Systems Quiz with Answers - 7
1. A system that provides segmentation without paging puts holes
in the physical address space, forcing the operating system to waste physical
memory.
(a)
TRUE (b) FALSE
Answer: FALSE.
Segmentation potentially puts holes in the VIRTUAL space, but doesn’t
require holds in the physical address space, since the segmentation mapping is
free to use any contiguous blocks of memory. [source:
UCB]
2. In a single processor system, the kernel can simply disable
interrupts to safely access kernel data structures, and does not need to use
any spin locks.
(a) TRUE (b)
FALSE
Answer: TRUE.
Spinlock results in an indefinite
postponement until the thread holding the lock can finish and release it. Using
spinlocks in multi-core processors are OK. [source:
IITB]
3. Memory mapped I/O devices cannot be accessed by user-level
threads.
(a)
TRUE (b) FALSE
Answer: FALSE.
Memory-mapped I/O is accomplished using load/store instructions to a special
region of memory; a user-level thread can access this region if the user’s page
table has a mapping for it. [source: UCB]
4. Consider N threads in a process that share a global variable
in the program. If one thread makes a change to the variable, the change is visible
to other threads.
(a) TRUE (b)
FALSE
Answer: TRUE.
The change will be visible to other
threads. This is logical, since the process is the unit of resource management,
not the thread. [source: IITB]
5. The rate of page faults in a virtual memory system can always
be reduced by adding more memory.
(a)
TRUE (b) FALSE
Answer: FALSE. There are
circumstances in which adding memory can actually increase the number of
faults. Specifically: Belady’s anomaly can come into play for a FIFO
replacement policy and certain access patterns. [source: UCB]
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