MS-DOS: Directory and Subdirectory Limitations

This article was previously published under Q39927
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In MS-DOS, hard disk and floppy disk root directories are limited in size,depending on the media type involved. However, subdirectories can containas many files as disk space allows.

The subdirectories are not fixed in size and can allocate new data clustersto hold additional directory entries. Thus, subdirectories can growdynamically as long as there are data clusters available to hold new fileand subdirectory entries. However, the root directory can hold only acertain number of subdirectory entries because it is fixed in size.
The following table shows the number of root directory entries for commonfloppy 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
Additional information is documented on page 27 of the "Quick ReferenceGuide to Hard Disk Management" printed by Microsoft Press.
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".

Article ID: 39927 - Last Review: 12/04/2015 09:03:17 - Revision: 2.0

  • Microsoft MS-DOS 3.1
  • Microsoft MS-DOS 3.2 Standard Edition
  • Microsoft MS-DOS 3.21 Standard Edition
  • Microsoft MS-DOS 3.3 Standard Edition
  • Microsoft MS-DOS 3.3a
  • Microsoft MS-DOS 4.0 Standard Edition
  • Microsoft MS-DOS 4.01 Standard Edition
  • Microsoft MS-DOS 5.0 Standard Edition
  • Microsoft MS-DOS 5.0a
  • Microsoft MS-DOS 6.0 Standard Edition
  • Microsoft MS-DOS 6.2 Standard Edition
  • Microsoft MS-DOS 6.21 Standard Edition
  • Microsoft MS-DOS 6.22 Standard Edition
  • Microsoft Windows 95
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