Department Of Computer Science & engineering  And IT
Class : CSE V & IT
Subject: Principals Of Operating Systems

Tutorial Sheet –4

Ql. Describe the following allocation algorithms
(a) First fit
(b) Best fit
(c) Worst fit

Q2. Explain Logical address & Physical Address with difference. (May 2001)

Q2. Given memory partitions of 100KB, 500KB, 200KB, 300KB and 6OOKB(in order), how would each of the first fit and worst fit algorithms place processes of 212KB,417KB, 112KB and 426KB(in order)? Which algorithm makes the most efficient use of memory?

Q3. Consider the following segment table:

Segment      Base              Length
0                    219                 600
1                    2300               14
2                    90                  100
3                   1327               580
4                   1952                96

What are physical addresses for the following logical addresses?
(a) 0430
(b) 110
(c) 2500
(d) 3400
(e) 4112

Q4. Consider a logical address space of eight pages of 1024 word each, mapped onto a physical memory of 32 frames
(a) How many bits is logical address?
(b) How many bits are in physical address?

Q5. Consider a paging system with the page table stored in memory
(a) If the memory reference takes 200 nanoseconds, how long does a paged memory reference take?
(b) If we add TLBs, and 75 percent of all page-table references are found in the TLBs, what is the effective memory reference time (Assume that finding page table entry in TLBs takes zero time. If try is there)