Windows command diskcomp command

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Compares the contents of two floppy disks. If used without parameters, diskcomp uses the current drive to compare both disks.


diskcomp [<drive1>: [<drive2>:]]


Parameter Description
<drive1> Specifies the drive containing one of the floppy disks.
/? Displays help at the command prompt.


  • The diskcomp command works only with floppy disks. You cannot use diskcomp with a hard disk. If you specify a hard disk drive for drive1 or drive2diskcomp displays the following error message:
    Invalid drive specification
    Specified drive does not exist
    or is nonremovable
  • If all tracks on the two disks being compared are the same (it ignores a disk’s volume number), diskcomp displays the following message:
    Compare OK

    If the tracks aren’t the same, diskcomp displays a message similar to the following:

    Compare error on
    side 1, track 2

    When diskcomp completes the comparison, it displays the following message:

    Compare another diskette (Y/N)?

    If you press Ydiskcomp prompts you to insert the disk for the next comparison. If you press Ndiskcomp stops the comparison.

  • If you omit the drive2 parameter, diskcomp uses the current drive for drive2. If you omit both drive parameters, diskcomp uses the current drive for both. If the current drive is the same as drive1diskcomp prompts you to swap disks as necessary.
  • If you specify the same floppy disk drive for drive1 and drive2diskcomp compares them by using one drive and prompts you to insert the disks as necessary. You might have to swap the disks more than once, depending on the capacity of the disks and the amount of available memory.
  • Diskcomp can’t compare a single-sided disk with a double-sided disk, nor a high-density disk with a double-density disk. If the disk in drive1 isn’t of the same type as the disk in drive2diskcomp displays the following message:
    Drive types or diskette types not compatible
  • Diskcomp doesn’t work on a network drive or on a drive created by the subst command. If you attempt to use diskcomp with a drive of any of these types, diskcomp displays the following error message:
    Invalid drive specification
  • If you use diskcomp with a disk that you made by using copydiskcomp might display a message similar to the following:
    Compare error on
    side 0, track 0

    This type of error can occur even if the files on the disks are identical. Although copy duplicates information, it doesn’t necessarily place it in the same location on the destination disk.

  • diskcomp exit codes:
    TABLE 2
    Exit code Description
    0 Disks are the same
    1 Differences were found
    3 Hard error occurred
    4 Initialization error occurred

    To process exit codes that are returned by diskcomp, you can use the ERRORLEVEL environment variable on the if command line in a batch program.


If your computer has only one floppy disk drive (for example, drive A), and you want to compare two disks, type:

diskcomp a: a:

Diskcomp prompts you to insert each disk, as needed.

To illustrates how to process a diskcomp exit code in a batch program that uses the ERRORLEVEL environment variable on the if command line:

rem Checkout.bat compares the disks in drive A and B
echo off
diskcomp a: b:
if errorlevel 4 goto ini_error
if errorlevel 3 goto hard_error
if errorlevel 1 goto no_compare
if errorlevel 0 goto compare_ok
echo ERROR: Insufficient memory or command invalid
goto exit
echo ERROR: An irrecoverable error occurred
goto exit
echo You just pressed CTRL+C to stop the comparison
goto exit
echo Disks are not the same
goto exit
echo The comparison was successful; the disks are the same
goto exit