Question
If the partitions are fixed and a new job arrives requiring 52 blocks of
main memory, show memory after using each of the following partition
selection approaches.
a) First fit
b) Best fit
c) Worst fit
main memory, show memory after using each of the following partition
selection approaches.
a) First fit
b) Best fit
c) Worst fit
Answers
Answered by
GPT-4o mini
To illustrate how the different partition selection approaches work when allocating memory to a new job that requires 52 blocks, I'll explain each method step-by-step. To begin, let's define an example set of partition sizes and visualize the memory before any job is allocated.
**Assumed Memory Partitions (in blocks):**
1. 10 blocks
2. 20 blocks
3. 30 blocks
4. 50 blocks
5. 60 blocks
6. 80 blocks
Now we have a list of partitions, and we will assign the new job requiring 52 blocks using each allocation method.
### a) First Fit
**First Fit Approach:**
- The first fit algorithm allocates the first available partition that is large enough to accommodate the job.
**Analysis:**
1. Check the first partition (10 blocks) - too small.
2. Check the second partition (20 blocks) - too small.
3. Check the third partition (30 blocks) - too small.
4. Check the fourth partition (50 blocks) - too small.
5. Check the fifth partition (60 blocks) - **Allocates** here.
**Memory after First Fit:**
- 10 blocks: 10
- 20 blocks: 20
- 30 blocks: 30
- 50 blocks: 50
- 60 blocks: 8 (60 - 52 = 8)
- 80 blocks: 80
---
### b) Best Fit
**Best Fit Approach:**
- The best fit algorithm searches for the smallest available partition that is large enough to accommodate the job, minimizing wasted space.
**Analysis:**
1. Check the first partition (10 blocks) - too small.
2. Check the second partition (20 blocks) - too small.
3. Check the third partition (30 blocks) - too small.
4. Check the fourth partition (50 blocks) - too small.
5. Check the fifth partition (60 blocks) - **Allocates** here (wastes 8 blocks).
**Memory after Best Fit:**
- 10 blocks: 10
- 20 blocks: 20
- 30 blocks: 30
- 50 blocks: 50
- 60 blocks: 8 (60 - 52 = 8)
- 80 blocks: 80
---
### c) Worst Fit
**Worst Fit Approach:**
- The worst fit algorithm searches for the largest available partition and allocates the required blocks there to leave the largest leftover space.
**Analysis:**
1. Check the first partition (10 blocks) - too small.
2. Check the second partition (20 blocks) - too small.
3. Check the third partition (30 blocks) - too small.
4. Check the fourth partition (50 blocks) - too small.
5. Check the fifth partition (60 blocks) - **Allocates** here (wasting 8 blocks).
**Memory after Worst Fit:**
- 10 blocks: 10
- 20 blocks: 20
- 30 blocks: 30
- 50 blocks: 50
- 60 blocks: 8 (60 - 52 = 8)
- 80 blocks: 80
---
### Summary of Allocations:
- **After First Fit:** Occupied partition is 60 (remaining 8).
- **After Best Fit:** Occupied partition is 60 (remaining 8).
- **After Worst Fit:** Occupied partition is 60 (remaining 8).
In this case, all three allocation strategies resulted in the same memory distribution after the job was allocated, since the only suitable partition available was 60 blocks. Therefore, the best fit and worst fit also ended up using the same partition as the first fit due to the specific sizes of our initial partitions.
**Assumed Memory Partitions (in blocks):**
1. 10 blocks
2. 20 blocks
3. 30 blocks
4. 50 blocks
5. 60 blocks
6. 80 blocks
Now we have a list of partitions, and we will assign the new job requiring 52 blocks using each allocation method.
### a) First Fit
**First Fit Approach:**
- The first fit algorithm allocates the first available partition that is large enough to accommodate the job.
**Analysis:**
1. Check the first partition (10 blocks) - too small.
2. Check the second partition (20 blocks) - too small.
3. Check the third partition (30 blocks) - too small.
4. Check the fourth partition (50 blocks) - too small.
5. Check the fifth partition (60 blocks) - **Allocates** here.
**Memory after First Fit:**
- 10 blocks: 10
- 20 blocks: 20
- 30 blocks: 30
- 50 blocks: 50
- 60 blocks: 8 (60 - 52 = 8)
- 80 blocks: 80
---
### b) Best Fit
**Best Fit Approach:**
- The best fit algorithm searches for the smallest available partition that is large enough to accommodate the job, minimizing wasted space.
**Analysis:**
1. Check the first partition (10 blocks) - too small.
2. Check the second partition (20 blocks) - too small.
3. Check the third partition (30 blocks) - too small.
4. Check the fourth partition (50 blocks) - too small.
5. Check the fifth partition (60 blocks) - **Allocates** here (wastes 8 blocks).
**Memory after Best Fit:**
- 10 blocks: 10
- 20 blocks: 20
- 30 blocks: 30
- 50 blocks: 50
- 60 blocks: 8 (60 - 52 = 8)
- 80 blocks: 80
---
### c) Worst Fit
**Worst Fit Approach:**
- The worst fit algorithm searches for the largest available partition and allocates the required blocks there to leave the largest leftover space.
**Analysis:**
1. Check the first partition (10 blocks) - too small.
2. Check the second partition (20 blocks) - too small.
3. Check the third partition (30 blocks) - too small.
4. Check the fourth partition (50 blocks) - too small.
5. Check the fifth partition (60 blocks) - **Allocates** here (wasting 8 blocks).
**Memory after Worst Fit:**
- 10 blocks: 10
- 20 blocks: 20
- 30 blocks: 30
- 50 blocks: 50
- 60 blocks: 8 (60 - 52 = 8)
- 80 blocks: 80
---
### Summary of Allocations:
- **After First Fit:** Occupied partition is 60 (remaining 8).
- **After Best Fit:** Occupied partition is 60 (remaining 8).
- **After Worst Fit:** Occupied partition is 60 (remaining 8).
In this case, all three allocation strategies resulted in the same memory distribution after the job was allocated, since the only suitable partition available was 60 blocks. Therefore, the best fit and worst fit also ended up using the same partition as the first fit due to the specific sizes of our initial partitions.