CITS2002 Systems Programming  
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File Allocation Methods - Indexed

The file allocation method of choice in both Unix and Windows is the indexed allocation method.

This method was championed by the Multics operating system in 1966. The file-allocation table contains a multi-level index for each file - just as we have seen in the use of inodes, which contain direct pointers to data blocks, and pointers to indirection blocks (which point to more data blocks).

Indexed Allocation with Block Portions

Indirection blocks are introduced each time the total number of blocks "overflows" the previous index allocation.

Typically, the indices are neither stored with the file-allocation table or with the file, and are retained in memory when the file is opened.

 

CITS2002 Systems Programming, Lecture 15, p11, 18th September 2023.