FORMAT and 8-Sector Disks in MS-DOS (69577)

The information in this article applies to:
    Microsoft MS-DOS operating system 4.0
    Microsoft MS-DOS operating system 4.01
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q69577


When you issue the MS-DOS version 4.x FORMAT command with any of the following parameters


FORMAT neither asks for a volume label nor places a BIOS parameter block (BPB) in the boot sector of the resulting disk. In MS-DOS 5.0 and later, if you issue the FORMAT command with any of the above parameters, FORMAT places a BPB in the boot sector, but the disk does not have a volume label.

NOTE: The switches in this list are mutually exclusive. In MS-DOS 6.0, 6.2, and 6.21, you must include a /t parameter with the /n parameter.


The MS-DOS 4.01 FORMAT utility does not place a BPB in the boot record when a disk is formatted to 8 sectors per track. Disks formatted with 8 sectors per track are considered to be destined for MS-DOS 1.0 compatibility and therefore do not have a defined BPB.

The FORMAT utility also does not ask for a volume label when a disk is formatted to 8 sectors per track. Like the BPB, a volume label is not defined for DOS version 1.0 disks.

The lack of a normal BPB can cause problems for some utility programs that try to read the disk directly. The information stored in a post-1.0 BPB provides information that helps these utilities to locate the FATs and the root directory. These utility programs cannot be used on 8-sector disks.

Because the lack of a BPB can cause problems for some utility programs, the FORMAT utility in MS-DOS versions 5.0 and later places a BPB in the boot record. Appropriate values are included in the BPB. However, the volume label prompt is still skipped, and the final disk has no volume label.

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB69577