Commodore 1581 - Creating a Relative File

where "file #" is the file number, normally an integer between 1 and
127; "device #" is the device number to be used, normally 8 on the
1581; "channel #" selects a particular channel along which communi
cations for this file can take place, normally between 2 and 14; "drive
#" is the drive number, always 0 on the 1581; and "file name" is the
name of the file, with a maximum length of 16 characters. Pattern
matching characters are allowed in the name when accessing an
existing file, but not when creating a new one. The record length is the
size of each record within the file in bytes used, including carriage
returns, quotation marks and other special characters.
-NOTE
• Do not precede the file name (in BASIC 7.0) or the
drive number (in BASIC 2.0) with the "at" sign (@); there is
no reason to replace a relative file.
• L record length (in BASIC 7.0) or, L ," + CHR$(rec-
ord length) (in BASIC 2.0) is only required when a relative
file is first created, though it may be used later, so long as
the record length is the same as when the file was first
created. Since relative files may be read from or written to
alternately and with equal ease, there is no need to specify
Read or Write mode when opening a relative file.
• "file #", "device #" and "channel #" must be valid
numeric constants, variables or expressions. The rest of the
command must be a valid string literal, variable or expres
sion. In BASIC 7.0 DOPEN, whenever a variable or expres
sion is used as a file name it must be surrounded by
parentheses.
EXAMPLES:
To create or reopen a relative file named "GRADES", of record
length 100, use: N
BASIC 7.0: DOPEN#2,"GRADES",L100,D0,U8
BASIC 2.0: OPEN 2,8,2,"GRADES,L," + CHR$(100)
To reopen an unknown relative file of the user's choice that has
already been created, use:
BASIC 7.0: 200 INPUT"WHICH FILE";FI$
210 DOPEN#5,(FI$),D0,U8
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