File System Interface and Implementation Questions and Answers

Answer: C

The file system's main purpose is to provide a structured way to store and access data.

A file system organises data on storage devices into named files and directories, keeps track of where each file's blocks are, and controls access, so programs and users can store and retrieve data by name.

Memory allocation, CPU scheduling and peripheral control are the jobs of the memory manager, the process scheduler and the device manager.

Answer: A

The method is contiguous allocation.

In contiguous allocation a file occupies consecutive blocks on the disk, so reading it in order needs little or no head movement between blocks. Any block can also be located directly from the start address and length. Both sequential and direct access are as fast as they can be.

Linked allocation scatters blocks and has to follow pointers one by one. Indexed allocation needs index block lookups, and its data blocks may also be scattered. Hashed allocation is a way of organising directories, not a file block allocation method.

Answer: C

The fastest direct access comes from hashing.

In a hashed (direct) file, a hash function turns the record key straight into the address where the record is stored, so a record can usually be reached in a single access without searching.

A sequential file must be read from the start until the record is found. An indexed file first looks the key up in an index and then goes to the record, which takes extra accesses. Linked organisation follows pointers from record to record, which is slower still.

Answer: A

The bit map needs one bit per block. The number of blocks is the disk size divided by the block size, and the space is that number of bits converted to bytes.

So 332.8 KB is right. The other figures are not near 1.3 x 2^18 bytes, and they would arise from mistakes in converting units.

Answer: C

The directory structure used in the Unix file system is a directed acyclic graph. Unix allows a file to have several links, so one file can appear in more than one directory, but cycles are not permitted. This is more general than a plain tree, where each file has a single parent.

A hierarchical or tree structured directory does not allow sharing of files through links, and a general graph structure would allow cycles, which Unix does not allow.