os question

Question

Consider the following statements:
1. Paging suffers from internal fragmentation and segmentation suffers from external fragmentation.
2. FIFO replacement policy ignores locality of reference.
3. The essential content(s) in each entry of page table are both virtual page number and page frame number.
4. There is no problem to use single level page table even if it is large size, because there is no overhead, to maintain large page table.
Which of the above statements are correct?

• Only 3 and 4
• Only 2 and 3
• Only 1 and 4
• Only 1 and 2

Answer 1

1----- yes the 1st  statement is true 

https://en.wikipedia.org/wiki/Fragmentation_(computing)#External_fragmentation

2---- yes, it ignores the loaclity of reference, it is one of the reasons for belads anamoly .As it doesnot consider any fact it just removes the pages in the order of First In First Out .

3----The essential contents are not  both virtual page number and page frame number , it is only virtual page number.As the page table entry consists of all the virtual page number , but not all virtual page numbers are mapped to page numbers.

4---- If we use a Single level page table, the space of page table of single process will be much larger as the page table must have all the entries, so to reduce space we have multi level page tables

Comments

The essential content(s) in each entry of page table is  page frame number.  not virtual page number.

Page table entry must contain page number.