VERIFY

Directs MS-DOS to verify that your files are written correctly 
to a disk and displays the status of verification. For example, 
you can use this command to make sure data is not written to a 
bad sector. You can use this command either at the command 
prompt or in your AUTOEXEC.BAT file.

Note: There are two states of VERIFY mode. Default is off. You 
can turn it on by using the VERIFY command. If you have turned it on, 
the data written to disk will be verified every time when COPY, 
XCOPY commands run. Also, when writing data to disk through 
the MS-DOS file system, the data are also verified. THIS WILL 
MAKE WRITING TO THE DISK MUCH SLOWER.

For more information, please refer to MS-DOS Help or Windows NT 
command line command help.