Commodore Plus 4 - Page 28

16 The BASIC Language
BACKUP Abbr. bA
BACKUP Ddrive TO Ddrive, ON Uunit
Duplicates an entire disk in a dual disk drive. BACKUP does not let you copy
just parts of disks or change the names of files or of the disk. Use the COPY
command to duplicate individual files or change file names. This command does
not work with single disk drives such as the 1541.
The disk you are copying is the "master" disk; you are copying from the master
TO the blank disk.
Cautions: 1. BACKUP headers the recipient disk before copying files from the master disk.
Since headering a disk erases all the information stored on the disk, do not
BACKUP onto a disk that contains files you want to keep. Use' a blank disk or
a disk that contains information you no longer need.
2. BACKUP does not affect files on the master disk. However, since BACKUP
does header the recipient disk, double check to be sure the master disk is in the
drive you name as the master drive in the BACKUP command. To avoid
accidentally backing up in the wrong direction, always put the master disk in
drive 0.
3. BACKUP copies files indiscriminately—errors and all. For this reason, many
programmers prefer to use the COPY command or a copy utility program to
duplicate disks. If the master disk contains errors, do not use BACKUP.
Parameters: D disk drive number TO D disk drive number, U unit number
1. Drive numbers are either 0 or 1. No other numbers are allowed. The first disk
drive number indicates which drive contains the master disk, whose contents
you are copying. You should always put the master disk in drive 0.
2. TO is part of the command and must be included.
3. The second disk drive indicates which drive contains the blank disk onto which
you are copying the information from the master disk. Always put the recipient
disk in drive 1.
4. Unit number is an optional parameter that you should rarely if ever need. Use it
only if you have more than one dual disk drive connected to your computer,
and you are using a device other than unit 8 in the backup procedure. You can
precede the unit number with ON, but ON is not required. The unit number
must be between 8 and 11.
Note: The drive and unit number parameters can be specified with a vari
able or expression in parentheses.
Examples: BACKUP BO TO Dl Copies all the files on the disk in drive 0 onto
the disk in drive 1.