Updated: April 17, 2012
Applies To: Windows Vista, Windows Server 2008, Windows Server 2012, Windows 8
Compares the contents of two floppy disks. If used without parameters, diskcomp uses the current drive to compare both disks.
For examples of how to use this command, see Examples.
diskcomp [<Drive1>: [<Drive2>:]]
Specifies the drive containing one of the floppy disks.
Specifies the drive containing the other floppy disk.
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 Drive2, diskcomp 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, diskcomp displays the following message:
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 the disk 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 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.
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.
Understanding diskcomp exit codes
The following table explains each exit code.
Disks are the same
Differences were found
Hard error occurred
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.
The following example 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 :ini_error echo ERROR: Insufficient memory or command invalid goto exit :hard_error echo ERROR: An irrecoverable error occurred goto exit :break echo "You just pressed CTRL+C" to stop the comparison goto exit :no_compare echo Disks are not the same goto exit :compare_ok echo The comparison was successful; the disks are the same goto exit :exit