Diskcomp

Article
08/31/2016

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.

Syntax

diskcomp [<Drive1>: [<Drive2>:]]

Parameters

Parameter	Description
<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.

Remarks

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 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.

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.

Exit code	Description
0	Disks are the same
1	Differences were found
3	Hard error occurred
4	Initialization error occurred

Examples

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

Additional references

Command-Line Syntax Key

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