Compares the contents of two floppy disks. Used without parameters, diskcomp uses the current drive for both disks that you want to compare.


diskcomp [drive1**:** [drive2**:**]]


drive1   : Specifies the drive containing one of the floppy disks.

drive2   : Specifies the drive containing the other floppy disk.

/?   : Displays help at the command prompt.


  • Using disks

    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 drive2, diskcomp displays the following error message:

    Invalid drive specification

Specified drive does not exist or is nonremovable

  • Comparing disks

    If all tracks on the two disks being compared are the same, diskcomp displays the following message:

    Compare OK

    If the tracks are not 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 Y, **diskcomp** prompts you to insert disks for the next comparison. If you press N, **diskcomp** stops the comparison.

When **diskcomp** makes the comparison, it ignores a disk's volume number.
  • Omitting drive parameters

    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 drive1, diskcomp prompts you to swap disks as necessary.

  • Using one drive

    If you specify the same floppy disk drive for drive1 and drive2, diskcomp does a comparison 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.

  • Comparing different types of disks

    Diskcomp cannot 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 is not of the same type as the disk in drive2, diskcomp displays the following message:

    Drive types or diskette types not compatible

  • Using diskcomp with networks and redirected drives

    Diskcomp does not 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

  • Comparing an original disk with a copy

    When you use diskcomp with a disk that you made by using copy, diskcomp 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 does not necessarily place it in the same location on the destination disk. For more information about comparing individual files on two disks by using **Fc**, see Related Topics.
  • Understanding diskcomp exit codes

    The following table lists each exit code and a brief description.

    Exit code



    Disks are the same


    Differences were found


    Hard error occurred


    Initialization error occurred

    To process exit codes returned by diskcomp, you can use errorlevel 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.

The following example illustrates how to process a diskcomp exit code in a batch program that uses the errorlevel parameter 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 

Formatting legend




Information that the user must supply


Elements that the user must type exactly as shown

Ellipsis (...)

Parameter that can be repeated several times in a command line

Between brackets ([])

Optional items

Between braces ({}); choices separated by pipe (|). Example: {even|odd}

Set of choices from which the user must choose only one

Courier font

Code or program output





Command-line reference A-Z