Q39927: MS-DOS: Directory and Subdirectory Limitations

Article: Q39927
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:3.x,4.x,5.x,6.0,6.2,6.21,6.22; WINDOWS:95
Operating System(s): 
Keyword(s): msdos win95
Last Modified: 17-DEC-2000

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The information in this article applies to:

- Microsoft MS-DOS operating system versions 3.1, 3.2, 3.21, 3.3, 3.3a, 4.0, 4.01, 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
- Microsoft Windows 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
  Iomega Zip disks (100 MB): 260

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.

Additional query 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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Keywords          : msdos win95 
Technology        : kbWin95search kbZNotKeyword3 kbMSDOSSearch kbMSDOS321 kbMSDOS400 kbMSDOS320 kbMSDOS330a kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS310 kbMSDOS500 kbMSDOS330 kbMSDOS401 kbMSDOS500a
Version           : MS-DOS:3.x,4.x,5.x,6.0,6.2,6.21,6.22; WINDOWS:95

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