BACKUP should not be run when an APPEND path is defined. Turn APPEND off 
(APPEND ;) first. Don't use BACKUP on ASSIGNed, JOINed, or SUBSTed drive 
letters.

The XCOPY command is an alternative way to backup files.  It has some 
limitations, but is frequently faster than the BACKUP command.
                                                                              
Unlike COPY and XCOPY, BACKUP does not have a /V option. Execute the VERIFY 
command to turn VERIFY ON before doing a backup if there is any question about 
the reliability of the destination diskettes. See the NEW_TERMS VERIFY topic 
for more information. 

You should have PLENTY of formatted diskettes before beginning a BACKUP
command. Remember that each Megabyte (million characters) of data to be
backed up requires one high-capacity diskette, or two (or more) double-
sided diskettes.

Using BACKUP and RESTORE is a way to copy a large file (greater than the size 
of a single diskette) from one computer to another.

BACKUP with one level of DOS will not necessarily create diskettes that 
RESTORE for another level of DOS can read. Use caution when changing levels 
of DOS. Run a few compatibility tests first. DOS 3.3 on most systems is a 
lot different than preceding levels of BACKUP.

BACKUP can handle lots of subdirectories and duplicate names (a file in two 
different directories with the same name). Older versions of BACKUP do this 
by creating unique extensions of the form .@nn on the destination diskettes, 
where nn is a sequential number starting at 01 assigned to each file on the 
backup diskette which has the same name as a file already backed up. Beginning
with DOS 3.3, a single BACKUP.001 file holds all the backed up files, and a
file called CONTROL.001 keeps track of their path names. 

Some versions of BACKUP may backup your system (hidden) files. If the RESTORE
that later reads the files restores them to the wrong place on the disk, you 
may not be able to boot your computer. 
