Q. Consider the following C code for process P1 and P2. a=4, b=0, c=0 (initialization)
P1 P2
if (a < 0) b = 10;
c = b-a; a = -3;
else
c = b+a;
If the processes P1 and P2 executes concurrently (shared variables a, b and c), which of the following cannot be the value of ‘c’ after both processes complete?

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Q. Which of the following is NOT a valid deadlock prevention scheme?

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Q. More than one word are put in one cache block to

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Q. Consider Peterson’s algorithm for mutual exclusion between two concurrent processes i and j. The program executed by process is shown below.

repeat
flag [i] = true;
turn = j;
while ( P ) do no-op;
Enter critical section, perform actions, then exit critical
section
flag [ i ] = false;
Perform other non-critical section actions.
until false;

For the program to guarantee mutual exclusion, the predicate P in the while loop should be.

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Q. Which combination of the following features will suffice to characterize an OS as a multi-programmed OS?

(a) More than one program may be loaded into main memory
at the same time for execution.
(b) If a program waits for certain events such as I/O,
another program is immediately scheduled for execution.
(c) If the execution of program terminates, another program
is immediately scheduled for execution.

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Q. Consider the following statements with respect to user-level threads and kernel supported threads

i. context switch is faster with kernel-supported threads
ii. for user-level threads, a system call can block the
entire process
iii. Kernel supported threads can be scheduled independently
iv. User level threads are transparent to the kernel

Which of the above statements are true?

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Q. The minimum number of page frames that must be allocated to a running process in a virtual memory environment is determined by

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Q. Consider a small two-way set-associative cache memory, consisting of four blocks. For choosing the block to be replaced, use the least recently used (LRU) scheme. The number of cache misses for the following sequence of block addresses is 8, 12, 0, 12, 8

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Q. Suppose that we have an ordered file with one million records, stored on a disk. The block size is 2048b, records are of fixed size and are unspanned. The record length is 256b., then what is the number of blocks required for the data file.

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Q. Let the ordering key field of the file is 10 bytes long and a block pointer is 6 bytes long and a primary index has been constructed for the file. Then to search a record using index how many block access are required??

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Q. Memory, also called random access memory, or RAM

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Q. CPU scheduling takes place when

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