Final answer:
In the First Come First Served (FCFS) disk scheduling algorithm, the seek time is equal to the total distance traveled. The seek time for the given pending requests is 352ms.
Step-by-step explanation:
The First Come First Served (FCFS) disk scheduling algorithm serves requests in the order they arrive. In this case, the pending requests are 10, 27, 16, 8, 36, 20, and 42. The current position of the disk arm is at cylinder 16.
To calculate the seek time, we need to calculate the distance between each request and sum them up. The seek time for the FCFS algorithm is equal to the total distance traveled.
- From 16 to 10: 6 cylinders (6 * 4ms per cylinder = 24ms)
- From 10 to 27: 17 cylinders (17 * 4ms per cylinder = 68ms)
- From 27 to 16: 11 cylinders (11 * 4ms per cylinder = 44ms)
- From 16 to 8: 8 cylinders (8 * 4ms per cylinder = 32ms)
- From 8 to 36: 28 cylinders (28 * 4ms per cylinder = 112ms)
- From 36 to 20: 16 cylinders (16 * 4ms per cylinder = 64ms)
- From 20 to 42: 22 cylinders (22 * 4ms per cylinder = 88ms)
Total Seek Time: 24ms + 68ms + 44ms + 32ms + 112ms + 64ms + 88ms = 352ms
In the First Come First Served (FCFS) disk scheduling algorithm, requests are served in the order they arrive. Let's calculate the seek time for the given sequence of disk requests.
Disk requests (in order from first arrived): 10, 27, 16, 8, 36, 20, 42
Initial position of the disk arm: 16
Previous request: 8
Seek time for each request is calculated as the absolute difference between the current cylinder and the requested cylinder. The seek time for the first request is calculated from the initial position of the disk arm to the first requested cylinder.
1. **Seek Time for Request 1 (10):**
- Absolute difference: |16 - 10| = 6 cylinders
- Seek time: 6 cylinders * 4ms/cylinder = 24ms
2. **Seek Time for Request 2 (27):**
- Absolute difference: |10 - 27| = 17 cylinders
- Seek time: 17 cylinders * 4ms/cylinder = 68ms
3. **Seek Time for Request 3 (16):**
- Absolute difference: |27 - 16| = 11 cylinders
- Seek time: 11 cylinders * 4ms/cylinder = 44ms
4. **Seek Time for Request 4 (8):**
- Absolute difference: |16 - 8| = 8 cylinders
- Seek time: 8 cylinders * 4ms/cylinder = 32ms
5. **Seek Time for Request 5 (36):**
- Absolute difference: |8 - 36| = 28 cylinders
- Seek time: 28 cylinders * 4ms/cylinder = 112ms
6. **Seek Time for Request 6 (20):**
- Absolute difference: |36 - 20| = 16 cylinders
- Seek time: 16 cylinders * 4ms/cylinder = 64ms
7. **Seek Time for Request 7 (42):**
- Absolute difference: |20 - 42| = 22 cylinders
- Seek time: 22 cylinders * 4ms/cylinder = 88ms
**Total Seek Time:**
- \( 24 + 68 + 44 + 32 + 112 + 64 + 88 = 432 \) milliseconds
Therefore, the total seek time needed for the given requests in the FCFS disk scheduling algorithm is 432 milliseconds.