Consider a disk queue with requests for $${\rm I}/O$$ to blocks on cylinders $$47, 38, 121, 191,$$ $$87, 11, 92, 10.$$ The $$C$$-$$LOOK$$ scheduling algorithm is used. The head is initially at cylinder number $$63,$$ moving towards larger cylinder numbers on its servicing pass. The cylinders are numbered from $$0$$ to $$199.$$ The total head movement (in number of cylinders) incurred while servicing these requests is _________________ .

Consider a main memory with five page frames and the following sequence of page references: 3, 8, 2, 3, 9, 1, 6, 3, 8, 9, 3, 6, 2, 1, 3. Which one of the following is true with respect to page replacement policies First In First Out (FIFO) and Least Recently Used (LRU)?

Suppose the following disk request sequence (track numbers) for a disk with 100 tracks is given:

45, 20, 90, 10, 50, 60, 80, 25, 70.

Assume that the initial position of the R/W head is on track 50. The additional distance that will be traversed by the R/W head when the Shortest Seek Time First (SSTF) algorithm is used compared to the SCAN (Elevator) algorithm (assuming that SCAN algorithm moves towards 100 when it starts execution) is____________ tracks.

A system contains three programs and each requires three tape units for its operation. The Minimum number of tape units which the system must have such that deadlocks never arise is _________.