1.Contiguous allocation: requires that each file occupy a set of contiguous blocks on the disk. Disk addresss define a linear ordering on the disk.

2.Linked allocation: solves all problems of contiguous allocation. With linked allocation, each file is a linked list of disk blocks; the disk blocks may be scattered anywhere on the disk. The directory contains a pointer to the first and last blocks of the file.

3.Indexed allocation: each file has its own index block, which is an array of disk