Technical question ans Operating Systems I 2016

Technical question ans Operating Systems I 2016.

Operating System
1) Abbreviate SPOOLING(not definition)?
Ans: Simultaneous Peripheral Operation On-line.
2) Explain overlapping w.r.t SPOOLING?
Ans: I/O of one job is overlapped with processing of another job.
3) Which of the following statements is not true?
a) Real time systems require rigid time requirements
b) Real time systems are used in complex applications
c) Real time systems don’t implement the concept of virtual memory most of the times
d) Real time systems have well defined constraints
e) None of these
Ans: (e)
4) What is the algorithm used by UNIX for cpu scheduling?
Ans: Simple Priority algorithm
5) What is the algorithm used by UNIX for worst case cpu scheduling?
Ans: Round-Robin algorithm
6) Which of the following is Not True.
a) Kernel is a program that is always running in a computer system
b) Kernel has a data structure called kernel stack in UNIX
c) A user process cannot preempt another user process
d) A process can make another process sleep
Ans: (d)
7) What is the difference between system call and function call? Ans:
System call is the interface between kernel and process where as function call is an
interface between the program and the function.
8) How many divisions are there in system calls and what are they?
Ans: 5 divisions
Process control
File manipulation
Device manipulation
9) Which of the following statements is CORRECT?
a) Job pool may hold more number of processes than can be accommodated in main memory
b) Job pool must hold as many processes as main memory can accommodate
c) Job pool cannot hold more number of processes than can be accommodated in main memory
d) Job pool always holds less number of processes than can be accommodated in main memory
Ans: (a)
10) Define critical region?
Ans: The section of code which causes inconsistency on execution of arbitrary I/o Interrupts
11) What is shared memory?
Ans: The common memory area used by process for communication between themselves
12) What is degree of multiprogramming?
Ans: Number of processes that can be executed simultaneously
13) Define semaphore?
Ans: Semaphore is variable used as a synchronization tool between processes that are running their critical regions.
14) What is the work done by execv system call?
Ans: It replaces the image memory space of the process with the object binary file of the one specified as an argument.
15) What is the maximum size of a file that UNIX can have?
a) 640 KB
b) 64 KB
c) 10 MB
d) 6 GB
e) 16 GB
Ans: (e)
16) A process can be divided into three regions what are they ?
Ans: Text, Data, Stack
17) Who controls degree of multiprogramming ?
Ans: Long term scheduler
18) What does medium term scheduler do ?
Ans: Swapping
19) What is a light weight process ?
Ans: Thread
20) What is the advantage of multiprogramming ?
Ans: Increases the efficiency of the CPU.
21) What is the main advantage of timesharing systems ?
Ans: Provides interaction between user and programs
22) What is symmetric multiprocessing ?
Ans: It is a multiprocessor system in which each processor runs an identical copy of os
23)Give an example for asymmetric multiprocessing system ?
Ans: Sun os ver 4.0
24) Give an example for symmetric multiprocessing ?
Ans: Encore’s version of UNIX.
25) What is the difference between trap and interrupt ?
Ans: Signal generated by hard ware or software is called interrupt, trap is a software generated interrupt
26) What is the difference between synchronous and asynchronous I/O ?
Ans: Sync I/O: control remains with the process until the completion of I/O Async I/O: returns the control without waiting for I/o completion
27) What is cache coherency ?
Ans: In multiprocessor system each processor has its own cache when all processors run concurrently changes to a variable in one cache must be reflected in all remaining caches
28) Two registers are used for memory protection what are they ?
Ans: Base and Limit registers
29) MS-DOS is written for Intel processor which has no mode bit what is that processor?
Ans: Intel 8088
30) MS-DOS is written in which language ?
Ans: Assembly language 8088

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