In this section of Operating System Main Memory – Memory Management.it contain Operating System Main Memory – Memory Fragmentation MCQs (Multiple Choice Questions Answers).All the MCQs (Multiple Choice Question Answers) requires in detail reading of Operating System subject as the hardness level of MCQs have been kept to advance level.
This MCQs section is mainly focused on below lists of topics
1.Memory Fragmentation
- Merging of free memory area
1.Boundy tags
2.Memory Compaction
2.Buddy System and Power of 2 Allocators.
- Buddy System Allocator
- Power of 2 Allocator
PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE
1. Memory fragmentation can be defined as
- The existence of usable area in the memory of computer system
- The existence of unusable area in the memory of computer system
- The existence of unreachable area in the memory of computer system
- None of the above
2. External fragmentation occurs when a
- memory area remain unused because it is too large to be allocated
- memory area remain unused because it is too small to be allocated
- More memory is allocated than requested by the process
- less memory is allocated than requested by the process
3. Internal fragmentation occurs when a
- memory area remain unused because it is too large to be allocated
- memory area remain unused because it is too small to be allocated
- More memory is allocated than requested by the process
- less memory is allocated than requested by the process
some of the memory allocated to process remain unused,which happens if a process is allocated more memory than it needed
4. memory fragmentation results in_______
- stack overflow
- page faults
- Better Utilization of memory
- poor utilization of memory
5. In External fragmentation,merging of free memory areas using boundary tags.which of the following statement stands TRUE.
- Boundary tags ,is a status descriptor for a memory area.
- It consists of an ordered pair giving allocation status of the area;whether it is free or allocated.
- Boundary tags are identical tags stored at the start and end of memory area.
- when an area of memory becomes free ,the kernel checks the boundary tags of its neighboring areas.
- 1,2 only
- 1,3 only
- 1,4 only
- 1,2,3,4
Boundary tags ,is a status descriptor for a memory area.
It consists of an ordered pair giving allocation status of the area;whether it is free or allocated.
Boundary tags are identical tags stored at the start and end of memory area.
when an area of memory becomes free ,the kernel checks the boundary tags of its neighboring areas.
6. A relation called the 50-percent rule holds
- When an area of memory is freed,the total number of free area in the system decreases by 1
- When an area of memory is freed,the total number of free area in the system increases by 1
- When an area of memory is freed,the total number of free area in the system remain the same depending on whether the area being freed has zero,two,or one free area as neighbors.
- All of the above
7. Which of following statements stands true of a relation called 50-percent rule.
- the number of free area is half the number of allocated area ie. m=n/2
- it helps in estimating the size of the free list
- it also gives us method of estimating the free area in the memory at any time
- if sf is the average size of free area of memory,the total free memory is sf×n/2
- 1 only
- 1,2 only
- 1,2,3 only
- 1,2,3,4
the number of free area is half the number of allocated area ie. m=n/2
it helps in estimating the size of the free list
it also gives us method of estimating the free area in the memory at any time
if sf is the average size of free area of memory,the total free memory is sf×n/2
8. In________memory binding are changed in such manner that all free memory area can be merged to form a single free memory area.
- Memory Paging
- Memory Swapping
- Memory Compaction
- Memory segmentation
It is achieved by packing all allocated areas towards once end of the memory.
9. Which of the following statements stands true for memory compaction method.
- it involves movement of code and data in the memory.
- it is feasible only if computer system provides relocation register;the relocation can be achieved by simply changing the address in the relocation register
- it does not involves movement of code and data in the memory
- it does not involves use of relocation register
- 1,2 only
- 3,4 only
- 2,3 only
- 1,4 only
Memory compaction is not simple as suggested.it involves movement of code and data in memoryin free list if process memory has free memory on either side of it.it needs to be relocated to execute correctly from the new memory area allocated to it.Relocation involves modification of all addresses used by a process,including address of heap-allocated data and address contained in the general purppose registers.it is feasible only if the computer system provides a relocation register;relocation can be achieved by simply changing the address in the relocation register.
10. Buddy system and power of 2 allocators leads to ___________
- External fragmentation
- Internal Fragmentation
- No fragmentation
- None of the above
it performs allocation of memory in blocks of a few standard sizes.this features leads to internal fragmentation because some memory in each allocated memory block may be wasted.
11. In the Binary buddy system the sizes of memory blocks are ___________ and separate free lists are maintained for blocks of ___________sizes.
- power of 2,same
- square of 2,same
- power of 2,different
- square of 2,different
12. Which of the following statement is true for buddy system allocators?
- Buddy System splits and recombines memory blocks in a predetermined manner during allocation and deallocation.
- No splitting of blocks takes place, also no effort is made to coalesce adjoining blocks to form larger blocks; when released, a block is simply returned to its free list.
- When a request is made for m bytes, the allocator first check the free list containing blocks whose size is 2i for the smallest value of i such that 2i ≥ m.if the free list is empty ,it checks the list containing blocks that are higher the next higher power of 2 in size on so on. an entire block is allocated to a request.
- When a request is made for m bytes. the system finds the smallest power of 2 that is ≥ m. Let this be 2i.if the list is empty, it checks the lists for block of size 2i+1.it takes one block off this list and splits it into two halves of size 2i.it put one of these blocks into the free list of size 2i,and uses the other block to satisfy the request.
- 1 only
- 1,2 only
- 2,3 only
- 1,4 only
Buddy System splits and recombines memory blocks in a predetermined manner during allocation and deallocation.
When a request is made for m bytes. the system finds the smallest power of 2 that is ≥ m. Let this be 2i.if the list is empty, it checks the lists for block of size 2i+1.it takes one block off this list and splits it into two halves of size 2i.it put one of these blocks into the free list of size 2i,and uses the other block to satisfy the request.
13. Which of the following statement is true for Power-of-2 allocators?
- Buddy System splits and recombines memory blocks in a predetermined manner during allocation and deallocation.
- No splitting of blocks takes place, also no effort is made to coalesce adjoining blocks to form larger blocks; when released, a block is simply returned to its free list.
- When a request is made for m bytes, the allocator first check the free list containing blocks whose size is 2i for the smallest value of i such that 2i ≥ m.if the free list is empty ,it checks the list containing blocks that are higher the next higher power of 2 in size on so on. an entire block is allocated to a request.
- When a request is made for m bytes. the system finds the smallest power of 2 that is ≥ m. Let this be 2i.if the list is empty, it checks the lists for block of size 2i+1.it takes one block off this list and splits it into two halves of size 2i.it put one of these blocks into the free list of size 2i,and uses the other block to satisfy the request.
- 1 only
- 1,2 only
- 2,3 only
- 1,4 only
No splitting of blocks takes place, also no effort is made to coalesce adjoining blocks to form larger blocks; when released, a block is simply returned to its free list.
When a request is made for m bytes ,the allocator first check the free list containing blocks whose size is 2i for the smallest value of i such that 2i ≥ m. If the free list is empty, it checks the list containing blocks that are higher the next higher power of 2 in size on so on. an entire block is allocated to a request.
14. The buddy and power of 2 allocators are faster than the first-fit ,best-fit, next-fit allocators
- TRUE
- FALSE
because they avoid searches in free lists
15. The power of 2 allocators is faster than the Buddy System allocators.
- TRUE
- FALSE
because it does not need to performs splitting and merging.
