File Directory Structures

Maps symbolic file names to logical disk blocks (physical disk addresses) : e.g. file in your account something.txt to drive 0, block 3 etc

• One level directory (flat structure) e.g. CP/M, RT 11
• Usually simple system holding subset of file attributes - address and access control information
• In Unix a flat file system maps index (i-node) number of addresses (mapping of a tree structure into a flat structure before performing the physical mapping)

  
Figure 1: Flat directory structure

• Two Level Directory Structure : Minimum requirement for multi-user systems
• Two levels of directories : a Master Directory containing one entry for every user of the system, and a User File Directory : with one entry per file
• User directories can get very long - and name clashes may occur (this is the equivalent of the one level directory structure above)

So what's the solution for having too many files ?
Better directory organisation dictates a tree structure

• Multi level Directory Structure (as in Unix, MS-DOS, Mac etc)

  
Figure 2: Multi Level directory structure