The description below is from the book DOS the Easy Way by Everett Murdock Ph.D.
CLICK HERE for information about downloading the book.
Type: External (5.0 and later)
UNFORMAT d: [/J][/L][/test][/partn][/P][/U]
Purpose: Used to undo the effects of formatting a disk.
The UNFORMAT command is used to recover files on a disk that have been
using the FORMAT command.
The UNFORMAT command cannot always recover all the files that were on a
that was accidentally formatted. To assure a better recovery of files on
formatted disk, use the MIRROR command.
drive Specifies the drive containing the disk to unformat.
/J - Checks the disk to determine if the MIRROR command has been used
file-recovery information on it. (In DOS Version 6, this program is
the DOS supplemental disk.)
/L - Used with the /partn parameter to tell DOS that there is no MIRROR
on the disk.
/P - Used to tell DOS to send any UNFORMAT messages to the printer.
/U - Used to tell DOS to recover files from a formatted disk without
MIRROR file information (starting with DOS Version 6, this option is no
/partn - Used to restore a corrupted partition table of a hard disk
This option requires a PARTNSAV.FIL file created by using the MIRROR
with the /PARTN option (starting with DOS Version 6, this option is no