CHKDSK (Check Disk) COMMAND

Purpose:  Checks specified disks, looks for errors in the file system and
          corrects them.

Syntax:   CHKDSK [/F/S/V /C<d1>: /U<d2>:] [[d3:] ...]

Type:     External command

Description:
     The CHKDSK without parameters will only check the information on the
disk and display messages about the errors, without making corrections. We
recommend you to use this command first without any switches. Sometimes,
slight corrections manually introduced by a specialist to the file system,
can restore lost clusters.

     The CHKDSK command also generates a small report on the disks under
check.  For example:

     CHKDSK 1.04 Copyright (C) PhysTechSoft ltd. 1993-1996

     Checking drive D:
     Serial number - 0054-2587 tools
     Volume in this drive - TOOLS

      52,340,736 bytes total disk space.
       1,937,408 bytes available on disk.
      50,403,328 bytes occupied on disk .

     The generated report and all error messages may be saved by redirecting
the output to a file:

      A:\chkdsk b: > a:\disk_a.txt

     Do not specify a file located on a drive under check, for it may cause
errors.

Parameters:

/F - During the disk check CHKDSK will correct all found errors. All
     corrections will be written to the disk, so it is reasonable to use the
     /C parameter to save the previous condition of the disk.

/C - CHKDSK will save the correction backup information  on a disk,
     specified after the parameter without space, to a file named:

     undo_(checked_disk).chk

     You should not save to the disk, which is under checking. This
     parameter may only be used together with the /F parameter.

     If the CHKDSK command detects "lost" clusters on the disk, you are
     prompted with a question: Convert lost clusters to files?  If you type
     "Yes" , the CHKDSK with /F parameter will write every cluster to a file
     named:

     FILEnnnn.PTS,

     where: nnnn - is a hexadecimal number, starting with 0000, FILEnnnn.PTS
     files are created in the main directory of the specified disk.  These
     files can be then viewed and used, if they contain useful information.

/S - During the disk check CHKDSK will use only the first FAT copy.

/U - With this parameter the CHKDSK will restore the initial condition of
     the disk if the corrections were made using the /C switch. A drive
     containing the backup information should be specified immediately
     after the /U key with no trailing spaces as:
     undo_(checked_disk).chk

     WARNING! If the disk has been modified after correcting the errors with
     the /F /C parameters, e.g. files were amended, deleted etc., then the
     /U parameter should not be used to avoid new errors.

/V - CHKDSK, will display all file names and their paths.

     During the check of a disk the system can find subdirectories,
containing invalid information. Here the user should specify, whether to
reform a corrupt directory into a file or to still consider it to be a
directory.  It is recommended to save it as a file for this would not cause
new errors if the disk checking is continued; while the files, located in a
"bad" directory, will become "lost". After completion of the command, they
can be found in the root directory of the checked disk, under names
automatically generated by the system.

Notes:

1. The CHKDSK command assumes the floppy disk to be checked is readily
   inserted in a disk drive.
2. The CHKDSK command doesn't work on drives, used in the SUBST and the JOIN
   commands.
3. CHKDSK corrects the detected errors with the switch /F only. If you have
   a very important information on the disk under check, we highly recommend
   you to use the command with /C parameter. It saves the previous condition
   of the disk, so that you will be able to restore the information
   corrected by CHKDSK. Having saved the information about corrections on
   the other disk, you should not then write or change anything on it.
   Otherwise, new mistakes can appear or the information on the disk can be
   corrupted, when you restore it with the /U parameter.

5. CHKDSK should not be used in multitask system environment, like WINDOWS,
   DESKview etc. Otherwise, the information on the disk can be corrupted.

Examples:

1.      A:>chkdsk a:
or
        A:>chkdsk

displays the condition of a floppy disk from the drive A:

2.      A:>chkdsk a: b: c: /f

checks the condition of disks A:, B: and C:, corrects all mistakes found in
the directory or FAT.

3.      A:>chkdsk b: c: /f /ca:

checks the condition of disks B: and C:, corrects all errors, found in
directories or FATs and saves initial condition on the disk A: to files:

        A:\>undo_b.chk  and
        A:\>undo_c.chk

4.      A:>chkdsk c: /ua:

restores the initial state of the disk C:


5.      A>chkdsk a: /v

checks the condition of the floppy disk from the drive A: and displays all
filenames and directories on this disk.