Reference no: EM132211481

Question: Write a program to simulate managing les on disk. De ne the disk as a onedimensional array disk of size numOfSectors*sizeOfSector, where sizeOfSector indicates the number of characters stored in one sector. (For the sake of debugging, make it a very small number.) A pool of available sectors is kept in a linked list sectors of three eld structures: two elds to indicate ranges of available sectors and one next eld. Files are kept in a linked list les of four eld structures: lename, the number of characters in the le, a pointer to a linked list of sectors where the contents of the le can be found, and the next eld.

1. In the rst part, implement functions to save and delete les. Saving les requires claiming a sucient number of sectors from pool, if available. The sectors may not be contiguous, so the linked list assigned to the le may contain several nodes. Then the contents of the le have to be written to the sectors assigned to the le. Deletion of a le only requires removing the nodes corresponding with this le (one from les and the rest from its own linked list of sectors) and transferring the sectors assigned to this le back to pool. No changes are made in disk.

2. File fragmentation slows down le retrieval. In the ideal situation, one cluster of sectors is assigned to one le. However, after many operations with les, it may not be possible. Extend the program to include a function together() to transfer les to contiguous sectors; that is, to create a situation illustrated in Figure below. Fragmented les le1 and le2 occupy only one cluster of sectors after together() is nished. However, particular care should be taken not to overwrite sectors occupied by other les. For example, le1 requires eight sectors; ve sectors are free at the beginning of pool, but sectors 5 and 6 are occupied by le2. Therefore, a le f occupying such sectors has to be located rst by scanning les.

The contents of these sectors must be transferred to unoccupied positions, which requires updating the sectors belonging to f in the linked list; only then can the released sectors be utilized. One way of accomplishing this is by copying from the area into which one le is copied chunks of sectors of another le into an area of the disk large enough to accommodate these chunks. In the example in Figure below, contents of le1 are rst copied to sectors 0 through 4, and then copying is temporarily suspended because sector 5 is occupied. Thus, contents of sectors 5 and 6 are moved to sector 12 and 14, and the copying of le1 is resumed.