Final answer:
To read the entire disk, which has 80,000 sectors, it takes 209,980 milliseconds or approximately 210 seconds. This includes the time for revolutions and cylinder switches, but not track switches which are instantaneous.
Step-by-step explanation:
To calculate the time to read the entire disk, we need to analyze the number of steps involved in reading all sectors on all tracks and cylinders, and then add up the time taken for each step.
- Calculating the number of sectors on the entire disk: With 500 cylinders, 10 tracks per cylinder, and 16 sectors per track, the total number of sectors is 500 * 10 * 16 = 80,000 sectors.
- Calculating revolution time for one track: Since it takes 40 msec for the disk to make one revolution, and there are 16 sectors per track, the time to read one track is 40 msec.
- Calculating the time to switch tracks: Switching between tracks on the same cylinder is instantaneous, so no additional time is required for this step.
- Calculating the time to switch cylinders: With 20 msec required to switch from one cylinder to the next, and 499 transitions between cylinders (since we don't need to switch to the first cylinder), the total cylinder switch time is 499 * 20 msec = 9980 msec.
- Adding up the times: Each cylinder contains 10 tracks, so the total read time without cylinder switching is (500 cylinders * 10 tracks/cylinder * 40 msec/track) = 200,000 msec. Adding the cylinder switch time gives a total of 200,000 msec + 9980 msec = 209,980 msec.
Therefore, it takes 209,980 msec, or approximately 210 seconds, to read the entire disk.