This article was previously published under Q69767
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The following is a brief explanation of the MS-DOS FORMAT, UNFORMAT,and MIRROR commands and how these three utilities interact with oneanother.
NOTE: MIRROR does not come with Microsoft MS-DOS 6.0, 6.2, or 6.21.
When you format a floppy disk in MS-DOS, the FORMAT command has a built-infeature that creates an image of the system area of the disk. This filecontains a copy of the disk's boot sector, file allocation table (FAT), androot directory.
WARNING: If insufficient space is available on the disk to create thisfile, the UNFORMAT information will not be saved.
This information is intended to be used for recovering from accidentalformats. UNFORMATting should be done as soon as possible after theaccidental format because each subsequent write to the disk reducesthe likelihood of a successful recovery.
The process of creating this UNFORMAT information is identical to runningthe MIRROR program on the disk. If MIRROR has been run prior to executingthe FORMAT command, both images are saved (once again, space permitting),and the UNFORMAT command will give you the option of choosing the MIRRORsave file to use for rebuilding. (Your options will be the LAST MIRRORimage created or the PRIOR MIRROR image created.) MIRROR files retain theirlocation on the disk even during the formatting procedure.
MIRROR tracks the image file with a control file (MIRORSAV.FIL). If noMIRROR control file can be located on a disk, UNFORMAT scans the disk for aMIRROR image file (MIRROR.FIL). If an image file cannot be located,UNFORMAT scans the disk for old subdirectories. Any subdirectories that arelocated are attached to the disk's root directory and given a name such asSUBDIR.1, SUBDIR.2, and so forth. The files within these subdirectories mayremain intact. (This is a last-resort recovery technique.)
When you format a disk using the /u switch, or if you perform a format thatchanges the size of the disk, all information on the disk is erased. Incases such as these, no UNFORMAT information is saved, and any MIRRORcontrol/image files that were on the disk are erased. As a result, it isnot possible to UNFORMAT this disk.
For specific information on using the FORMAT, UNFORMAT, and MIRRORcommands, please see your printed MS-DOS documentation or MS-DOS Help.