Commodore Plus 4 - Programming modes

BASIC Version 3.5 Commands, Functions, and System Variables 65
Parameters: logical file number, device number, secondary address, "file name"
1. The logical file number can be from 1 to 255. Normally, use 1 to 127. For
some devices, 0 is a valid logical file number. Logical file numbers greater than
127 cause a line feed character to be sent after the carriage return at the end of
each line. Some non-Commodore printers or RS232 devices may require this.
The file number is not actually a part of the file or device you are opening. The
file number is just a temporary number used until you CLOSE the file. It gives the
computer a way to keep track of which device or file you are accessing. The file
number is like a number you take at a deli counter or laundry—it is associated
with you and your order only while your business is being transacted.
Once the device or file is OPEN, you must use the same file number for the
device or file when you address other commands to it. These other commands are
CLOSE, CMD, GET#, INPUT#, PRINT#, and PRINT# USING. Once the file
is CLOSEd, the logical file number is no longer associated with the file and you
do not have to use the same logical file number the next time you OPEN the file.
2. The device number identifies the other end (device or file) of the communi
cation channel you are opening through the computer. If you are accessing a disk
file, use the disk drive device number; if you are accessing a tape file, use the
cassette recorder device number, and so on.
Use these device numbers:
0
1
2
3
4-5
keyboard
cassette recorder
RS232 port
screen
printer (default is 4)
8-11 disk drive (default is 8)
3. The meaning of the secondary address depends on the device you are
accessing.
• For a cassette recorder, there are three: 0 (read from tape), 1 (write to tape and
close with end-of-file marker), or 2 (write to tape and close with end-of-tape
marker). The default is 0.
• For a printer, you can use secondary addresses to send commands. For more
information, see Chapter 6 and the printer manual; these commands differ
according to printer brand and type.
• For a disk drive, a secondary address names the channel being used. For more
information, see Chapter 6 and the disk drive manual.