OPERATING SYSTEM

Which of the following page replacement algorithms suffers from Belady's anomaly?
(i) Optimal replacement
(ii) LRU
(iii) FIFO
(iv) Both (a) and (c)

Compaction is used to solve the problem of
(i) External fragmentation
(ii) Internal fragmentation
(iii) both (i) and (ii)
(iv) None of these

Compaction is used to solve the problem of
(i) external fragmentation
(ii) internal fragmentation
(iii) both (a) and (c)
(iv) None of these

What is the difference between a page and a frame?

In contiguous memory allocation
(i) each process is contained in a single contiguous section of memory
(ii) all processes are contained in a single contiguous section of memory
(iii) the memory space is contiguous
(iv) None of the above

The address loaded into the memory address register of the memory is referred to as
(i) Physical address
(ii) IP address
(iii) Port address
(iv) Logical address

The CPU utilization when the system is ______
(i) timesharing
(ii) thrashing
(iii) multiprocessing
(iv) None of the above

If the size of logical address space is 2^m, and a page size is 2^n addressing units, then the high order bits of a logical address designate the page number, and the low order bits designate the page offset.
(i) m, n
(ii) n, m
(iii) m-n, m
(iv) m-n, n

Physical memory is broken into fixed-sized blocks called
(i) frames
(ii) pages
(iii) backing store
(iv) None of the above

Answer the following with justifications:
(i) Does swapping improve or degrade the efficiency of system utilization?
(ii) Can swapping be used in a multi-programming system?

What are the various allocation policies in variable partition multiprogramming? Explain the differences between internal and external fragmentations.

What do you understand by address binding? Explain the various address binding schemes.

What is the difference between fixed partition and variable partition also explains the need of compaction.

What is virtual memory? How is it implemented? Explain TLB in virtual memory with neat diagram.

What is Belady's Anomaly? Why LRU and Optimal Page Replacement algorithm doesn't suffer from this problem.

How many page faults would occur for the following reference string for four page frames and three page frames using LRU and FIFO algorithms:
1, 2, 3, 4, 5, 5, 3, 4, 1, 6, 7, 8, 7, 8, 9, 7, 8, 9, 5, 4, 5, 4, 2.

Consider the following page reference string: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1. How many page faults would occur for the following replacement algorithms? Assuming 3 frames are available. Also assume that initially none of pages in main memory.
(i) Optimal replacement
(ii) FIFO replacement

Consider the following page reference string: 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6.
Compare the page faults occur for the following replacement algorithms using 3 frames? Assume, initially all the frames are empty.
(i) LRU replacement
(ii) FIFO Replacement

Consider a simple paging system with the following parameters:

• 2^32 bytes of physical memory
• Page size of 2^10 bytes
• 2^16 pages of logical address space

(i) How many bits are in a logical address?
(ii) How many bytes are in a frame?
(iii) How many bits in the physical address specify the frame?
(iv) How many entries are in the page table?

Given five memory partitions of 100 KB, 500 KB, 200 KB, 300 KB and 600 KB (in order). How would the first-fit, best-fit, and worst-fit algorithms place processes of 212 KB, 417 KB, 112 KB and 426 KB (in order)? Which algorithm makes the most efficient use of memory?

Consider a demand-paging system with a paging disk that has an average access and transfer time of 20 milli-seconds. Addresses are translated through a page table in main memory, with an access time of 1 microsecond per memory access. Thus, each memory reference through the page table takes two accesses. To improve this time, we have added an associative memory that reduces access time to one memory reference if the page-table entry is in the associative memory.
Assume that 80 percent of the accesses are in the associative memory and that of those remaining, 10 percent (or 2 percent of the total) cause page faults. What is the effective memory access time?

Write short note on: Segmentation

Write short note on: Thrashing