target:Effective use of disk space;Quick access to files.

There are three common allocation methods:Continuous distribution,Link assignment,Index assignment

 

Extended Continuous Assignment Method:

Many new file systems adopt a modified continuous allocation method

Extension is a continuous disk block

When files are allocated, extensions are allocated to files

Another large continuous space

A file includes one or more extensions

Need a pointer to the next extension

The location of the file block becomes the start address, the number of blocks, plus a pointer to the next extension.

When allocating disk blocks, it is done in an extension