Commodore 128 Programmer's Reference Manual page 37

BASIC BUILDING BLOCKS AND BASIC 7.0 ENCYCLOPEDIA 27
Variable refers to any valid BASIC variable names, such as X, A$, T%, etc.
Expression refers to any valid BASIC expressions, such as A + B + 2,.5*(X + 3),
H etc.
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NOTE: For all DOS commands, variables and expressions used as
arguments must be endorsed in parentheses.
BASIC COMMANDS AND
STATEMENTS
APPEND
Append data to the end of a sequential file
APPEND #logical file number,"filename"[,Ddrive number][<ON|,>Udevice]
EXAMPLES:
Append # 8, "MYFILE" OPEN logical file 8 called "MYFILE", and prepare
to append with subsequent PRINT # statements.
Append #7,(A$),D0,U9 OPEN logical file named by the variable in A$ on
drive 0, device number 9, and prepare to APPEND.
AUTO
Enable/disable automatic line numbering
AUTO [line#]
EXAMPLES:
AUTO 10 Automatically numbers program lines in increments of 10.
AUTO 50 Automatically numbers lines in increments of 50.
AUTO Turns off automatic line numbering.
BACKUP
Copy the entire contents from one disk to another on a dual disk drive
BACKUP source Ddrive number TO destination Ddrive number [<ON|,>
Udevice]
NOTE: This command can be used only with a dual-disk drive.