University of Delhi 2010-2nd Sem M.C.A 1st yr Advanced Operating Systems UNIVERSITY - Question Paper
1 his question paper contains 2 printed pages
Your Roll No
6259
M. Sc. Computer Science / II Sem.
MCS - 202 - Advanced Operating Systems (Admissions of 2009 and onwards)
lime 2 hows Maximum Marks 50
{Wnte \our Roll No on the top immediately on receipt of this question paper) Attempt all questions Parts of a question should be answered together
Q1 a Differentiate between interrupts and exceptions (2)
b Give the disk layout of Unix file system, describing each component (5)
c What is the function of brelse algorithm7 Why is it essential to raise processor execution level in the brelse7 (3)
Q2 a Consider ihe part of the iget algorithm given below while (not done){
if (inode in inode cache) { if (mode locked) {
sleep (event mode becomes unlocked), continue, /* loop back to while */
}
What is the need for a process to start the loop from the beginning again (refer to comment above in the code), if mode is already there in the mode cache7 (3)
b Using system calls other than the readQ system call, write a function that returns the size of the file whose name is passed to it as an argument (4)
c The kernel maintains an exhaustive list of free disk blocks but not of the tree modes on the disk Give reasons (3)
Q3 a What is wrong if mknod() system call is used to create a directory7 (2)
b Consider the following program segment. main(mt ac, char *av[j) [ if (ac != 2){
cout "U<age " av[0] <"< " <uircctor> uar,t>'\ exit(l);
}
if (chdir(av[l J) = = -1)
cout av[l] " is not a directory".
}
Suppose the name of the executable file for the above program is chfoDir For the following sequence of commands
/usr/Progs> chi oDir OSProgs XXX>
displayed at XXX and why7 (3)
c Explain with the help of an example, how the order of writes to the disk can minimize the corruption of file system m the event of system failure (5)
Q4 a Explain what happens when a process wants to write data to a pipe that does not have enough space for the data to be written (4)
b The kernel does not allow the mount to succeed if the inode reference count of the directory at which mounting is to take place is greater than one Give an example to show that if this is not followed then it may result m an error/security lapse (3)
c Given the command as Is ~l my File, the permissions of myFile are shown as rws--x-x. What is the significance of * s in the permissions9 What will happen when
someone executes this file as $myFi!c-r' (3)
Q5 a Describe the three components of the context of a process. (6)
b Bnefl) explain what is per piocess region table and how is it related to the region lable(4)
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