Exam 2026-2027 Actual Complete Real Exam Questions
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Weird thing in FIFO were even if the number of frames
increases, there are always situations were the fault rate
increases - ANSWER-Belady's anomaly
Real time systems in which a missed deadline results in a
disaster - ANSWER-
Hard real
time
Real time systems in which a missed deadline results in
an annoyance -
ANSWER-Soft real
time
When can we schedule dynamic real time systems? Use
c as the tasks
compute time and p as the tasks period -
ANSWER-∑(c/p) ≤ 1
,__________ is when a low priority task blocks a high priority
task - ANSWER-
Priority
inversion
How can we solve priority inversion? - ANSWER-Grant low
priority task temp
promotion to
resolve
A _______ (lightweight process) is part of a process that has its
own execution
history, program counter, and stack -
ANSWER-Thread
What elements are unique to a process but not a thread? -
ANSWER-Text,
data, and
heap
Benefits of threads over processes - ANSWER-Lower mem
cost, information sharing, reduced creation/destruction time,
and reduced context switch time (to a sibling thread)
_____ space threads are supported by the OS, _______
space threads are
implemented in a library - ANSWER-
Kernel, user
,Threads which have separate thread table stored in the kernel.
Threads can be
run in multiple CPUs - ANSWER-
Kernel space
Threads which have thread table stored in each process -
ANSWER-User
space
In which space does a syscall in a thread block all other sibling
threads? Why? -
ANSWER-User bc kernel can't see threads and the entire
process is run in 1
CPU
In which space can you switch from executing a thread in
process A to a thread
in process B at any point (with a context switch)? -
ANSWER-Kernel
IPC in which process directly writes to a shared memory
space. Requires
programmer support - ANSWER-
Shared memory
IPC which avoids memory specific problems and handle
synchronization issues. Needs library or OS support and some
assembly - ANSWER-Message passing
, Examples of message passing systems - ANSWER-Pipes and
networks
Message passing system which can be named/unnamed. They
are created on
the fly for use by localhost and are set and used -
ANSWER-Pipes
Message passing system which uses TCP/UDP to
communicate host to host -
ANSWER-
Networks
Which IPC system can result in race conditions - ANSWER-
Message passing
Regions of code that we must protect - ANSWER-Critical region
What 4 rules must we maintain to avoid race conditions -
ANSWER-1) No assumptions may be made about speed or #
of CPUs (concurrency) 2) No two processes may be
simultaneously within their related CRs (safety)
3) No process running outside CR may block other processes
inside it (liveness)
4) No process should have to wait forever to enter its critical
region (liveness)