MS-DOS: Directory and Subdirectory Limitations (39927)

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