GATE CS Operating System questions

Practise Operating System questions for GATE CS. Explore official PYQs and original subject-wise quizzes, check answers and view available solutions. Free, no sign-in.

Trace the state changes explicitly. For scheduling, memory and synchronisation questions, record the given policy before calculating the result.

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SubjectTopicYearType

512

GB hard disk with

32

storage surfaces. There are

4096

sectors per track and each sector holds

1024

bytes of data. The number of cylinders in the hard disk is _________.

Consider the following code snippet using the fork () and wait () system calls. Assume that the code compiles and runs correctly, and that the system calls run successfully without any errors. int x=3; while (x>0){ fork (); printf("hello"); wait (NULL) ; X-- ; } The total number of times the printf statement is executed is __________.

Consider a memory management system that uses a page size of

2 \mathrm{~KB}

. Assume that both the physical and virtual addresses start from

0

. Assume that the pages

0,1,2

3

are stored in the page frames

1,3,2

0

, respectively. The physical address (in decimal format) corresponding to the virtual address

2500

(in decimal …

Which of the following tasks is/are the responsibility/responsibilities of the memory management unit

\text{(MMU)}

in a system with paging-based memory management?

Consider a process

\text{P}

\text{CPU}

. Which one or more of the following events will always trigger a context switch by the

\text{OS}

that results in process

\mathrm{P}

moving to a non-running state (e.g., ready, blocked)?

Consider a single processor system with four processes

\text{A, B, C,}

\text{D}

, represented as given below, where for each process the first value is its arrival time, and the second value is its

\text{CPU}

\mathrm{A}(0,10), \mathrm{B}(2,6), \mathrm{C}(4,3)

\mathrm{D}(6,7)

. Which one of the following options …

Consider a multi-threaded program with two threads

\mathrm{T} 1

\mathrm{T} 2

. The threads share two semaphores:

s1

(initialized to

1

s2

(initialized to

0

). The threads also share a global variable

\mathrm{x}

(initialized to

0

). The threads execute the code shown below. //code of T 1 wait (s1); x = x+1; print (x); …

Consider a disk with the following specifications: rotation speed of

6000

RPM, average seek time of

5

500

512

-byte sectors. A file has content stored in

3000

sectors located randomly on the disk. Assuming average rotational latency, the total time (in seconds, rounded off to

2

decimal places) to read the …

32

-bit system with

4 \mathrm{~KB}

page size and page table entries of size

4

bytes each. Assume

1 \mathrm{~KB}=2^{10}

bytes. The OS uses a

2

-level page table for memory management, with the page table containing an outer page directory and an inner page table. The

\text{OS}

allocates a page for the outer page directory upon …

Which one or more of the following need to be saved on a context switch from one thread

\text{(T1)}

of a process to another thread

\text{(T2)}

of the same process?

Which one or more of the following options guarantee that a computer system will transition from user mode to kernel mode?

Which one or more of the following

\text{CPU}

scheduling algorithms can potentially cause starvation?

Consider the two functions

\textsf{incr}

\textsf{decr}

shown below. incr(){ decr(){ wait(s); wait(s); X = X+1; X = X-1; signal(s); signal(s); } } There are

5

threads each invoking

\textsf{incr}

3

threads each invoking

\textsf{decr}

once, on the same shared variable

\mathrm{X}

. The initial value of

\mathrm{X}

Consider a computer system with

57

-bit virtual addressing using multi-level tree-structured page tables with

\mathrm{L}

levels for virtual to physical address translation. The page size is

4 \mathrm{~KB}(1 \mathrm{~KB}=1024 \mathrm{~B})

and a page table entry at any of the levels occupies

8

bytes. The value of

\mathrm{L}

Consider the following two-dimensional array

\text{D}

\text{C}

programming language, which is stored in row-major order: int D[128][128]; Demand paging is used for allocating memory and each physical page frame holds

512

elements of the array

\text{D}.

The Least Recently Used

\text{(LRU)}

page-replacement policy is used by the …

Consider the following threads,

\text{T}_{1}, \text{T}_{2},

\text{T}_{3}

executing on a single processor, synchronized using three binary semaphore variables,

\text{S}_{1}, \text{S}_{2},

\text{S}_{3},

operated upon using standard

\textsf{wait}()

\textsf{signal}().

The threads can be context switched in any order and at any …

Which of the following statements is/are

\text{TRUE}

with respect to deadlocks?

Which one of the following statements is

\text{FALSE}?

Consider four processes

\text{P, Q, R,}

\text{S}

\text{CPU}

as per round robin algorithm with a time quantum of

4\text{ units.}

The processes arrive in the order

\text{P, Q, R, S,}

\text{t = 0}.

There is exactly one context switch from

\text{S}

\text{Q},

exactly one context switch from …

Consider two files systems

\text{A}

\text{B}

, that use contiguous allocation and linked allocation, respectively. A file of size

100

blocks is already stored in

\text{A}

\text{B}

. Now, consider inserting a new block in the middle of the file (between

50^{th}

51^{st}

block), whose data is already available in …