  
PSS ID Number: Q39927
Article last modified on 09-12-1995
PSS database name: MSDOS
 
3.x 4.x 5.x 6.00 6.20 6.21 6.22 & 95
 
MS-DOS
 
Directory and Subdirectory Limitations

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The information in this article applies to:
 
 - Microsoft MS-DOS operating system versions 3.x, 4.x, 5.x, 6.0,
   6.2, 6.21, 6.22 & 95
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SUMMARY
=======
 
In MS-DOS, hard disk and floppy disk root directories are limited in size,
depending on the media type involved. However, subdirectories can contain
as many files as disk space allows.
 
The subdirectories are not fixed in size and can allocate new data clusters
to hold additional directory entries. Thus, subdirectories can grow
dynamically as long as there are data clusters available to hold new file
and subdirectory entries. However, the root directory can hold only a
certain number of subdirectory entries because it is fixed in size.
 
MORE INFORMATION
================
 
The following table shows the number of root directory entries for common
floppy and hard disk types:
 
   Single-sided 5.25-inch 180K floppy disks: 64
   Double-sided 5.25-inch 320K floppy disks: 64
   Double-sided 5.25-inch 360K floppy disks: 112
   Double-sided 3.5-inch 720K floppy disks: 112
   Double-sided 5.25-inch 1.2-megabyte floppy disks: 224
   Double-sided 3.5-inch 1.44-megabyte floppy disks: 224
   Hard disks (12- and 16-bit FATs): 512
 
MS-DOS version 3.3 added the following:
 
   Double-sided 3.5-inch 1.44-megabyte floppy disks
 
MS-DOS version 5.0 added the following:
 
   Double-sided 3.5-inch 2.88-megabyte floppy disks: 240
 
Windows 95 added the following:
 
    Long filename support. Root directory entries have the same
    limitations in Windows 95 as they do in previous versions of
    MS-DOS. If long filename support is enabled, then each file
    can use more than one directory entry (depending on the
    length of the filename, its case, and the characters it uses).
    Therefore, it is possible to run out of root directory entries
    with fewer than 512 files in the root directory of a hard disk, and
    fewer than the numbers specified above for floppy disks.
 
    For more information about long filenames and Windows 95, query on
    the following words in the Microsoft Knowledge Base:
 
       windows and 95 and long and filename and root and directory
 
REFERENCES
==========
 
Additional information is documented on page 27 of the "Quick Reference
Guide to Hard Disk Management" printed by Microsoft Press.
 
KBCategory: kbenv
KBSubcategory: msdos
Additional reference words: 3.20 3.21 3.30 3.30a 4.00 4.01 5.00 5.00a 6.00
6.20 6.21 6.22 sector format limit floppies "Cannot make directory entry".
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Copyright Microsoft Corporation 1995.


 
