Commodore 1581 - Page 48

NOTE
In the last chapter you learned how to check for disk
errors after disk commands in a program. It is equally
important to check for disk errors after using file-handling
statements. Failure to detect a disk error before using an
other file-handling statement could cause loss of data, and
failure of the BASIC program.
The easiest way to check the disk is to follow all file-
handling statements with a GOSUB statement to an error
check subroutine.
EXAMPLE:
BASIC 7.0
840 DOPEN#4,"DEGREE DAY DATA",D0,U8,W
850 GOSUB 59990: REM CHECK FOR DISK ERRORS
BASIC 2.0
840 OPEN 4,8,4,"0:DEGREE DAY DATA,S,W"
850 GOSUB 59990:REM CHECK FOR DISK ERRORS
FORMAT FOR THE DISK OPEN STATEMENT FOR SEQUENTIAL FILES:
BASIC 7.0
DOPEN#file#, "file name" [,Ddrive#] [,Udevice#] [,W]
BASIC 2.0
OPEN file #, device #, channel #,"drive #:file name,file type,-
direction"
where:
"file #" is an integer (whole number) between 1 and 255. Do not
open a disk file with a file number greater than 127 it will cause severe
problems. After the file is open, all other file commands will refer to it
by the number given here. Only one file can use any given file number
at a time.
"device #" is the number, or primary address, of the device to be
used. This number is an integer in the range 8-11, and is normally 8 on
the 1581.
"channel #" is a secondary address, giving further instructions to
the selected device about how further commands are to be obeyed. In
disk files, the channel number selects a particular channel along which
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