OS Test 1

What is the correct boot process order?

1.OS Initializing itself

2.Loading the OS

3.BIOS checking hardware (POST)

4.Load the Shell/GUI (DOS Prompt)

• 1,2,3,4

• 2,3,4,1

• 3,2,1,4

• 3,1,2,4

Once the initial diagnostics are performed and assigning system resources, the startup BIOS program will check for information about secondary storage devices that might contain the OS. This list of devices and the order in which they should be checked are found and arranged in the CMOS setup utility, and are commonly referred to as:

• The Boot Record

• The Boot sequence

• The MBR (Master Boot Record)

• The Disk Partition table

Which one or more of the following need to be saved on a context switch from one thread (T1) of a process to another thread (T2) of the same process?

• Program Counter

• Page table base Register

• Stack Pointer

• General Purpose Registers

When the result of a computation depends on the speed of the processes involved there is said to be

• A time clock

• Cycle Stealing

• Race Condition

• Deadlock

Consider a process P running on a CPU. Which one or more of the following events will always trigger a context switch by the OS that results in process P moving to a non-running state (e.g., ready, blocked)?

• P makes a blocking system call to read a block of data from the disk

• An interrupt is raised by disk to deliver the data requested by some other process

• P tries to access the instructions that is in secondary memory space, triggering a instruction fault

• A time interrupt is raised by the hardware

Consider four processes P, Q, R and S scheduled on a CPU as per round robin algorithm with a time quantum of 4 units. The processes arrive in the order P, Q, R, S, all at time t = 0. There is exactly one context switch from S to Q, exactly one context switch from R to Q, and exactly two context switches from Q to R. There is no context switch from S to P. Switching to a ready process after the termination of another process is also considered a context switch. Which one of the following is NOT possible as CPU burst time (in time units) of these processes?

• P=4, Q=10, R=6, S=2

• P=3, Q=7, R=7, S=3

• P=2, Q=9, R=5, S=1

• R=4, Q=12, R=5, S=4

Consider three concurrent processes P1, P2 and P3 as shown Figure, which access a shared variable D that has been initialized to 100. The process are executed on a uniprocessor system running a time-shared operating system. If the minimum and maximum possible values of D after the three processes have completed execution are X and Y respectively, then what will be the value of Y–X.

The following two functions P1 and P2 that share a variable B with an initial value of 2 execute concurrently.

P1( ) {

C = B – 1;

B = 2*C;

}

P2( ) {

D = 2 * B;

B = D - 1;

}

what is the number of distinct values that B can possibly take after the execution.

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--;

}

Howmany number of times the hello will printed on the console

The following C program is executed on a Unix/Linux system:

#include < unistd.h >

int main () {

int i ;

for (i=0; i<10; i++)

if (i%2 == 0)

fork ( ) ;

return 0 ;

}

The total number of child processes created with above code snippet.

• 31

• 15

• 63

• 32