From: Greg King (gngking_at_erols.com)
Date: 2006-04-21 13:50:31
Think about FOR...NEXT loops in BASIC. When you use several of them
together, they must be "nested:"
FOR X -------+
FOR Y -----+ |
FOR Z ---+ | |
...... | | |
NEXT Z --+ | |
NEXT Y ----+ |
NEXT X ------+
The policy is LIFO (Last-In, First-Out).
That same policy is needed for file control:
OPEN ------------+
CHKIN/CHKOUT --+ |
............ | |
CLRCHN --------+ |
CLOSE -----------+
---------------------------------------------------------
When we write Machine Language code for file operations, it helps to
remember how we do it in BASIC:
OPEN 15,8,15
INPUT#15,A,B$,C,D
CLOSE 15
OPEN 15,8,15 is the same as OPEN 15,8,15,"". If FNLEN ($b7) weren't zero,
then we would have OPEN 15,8,15,"<garbage>". If you remember that one way
to send DOS commands is:
OPEN 15,8,15,"<command>": CLOSE 15
then you can see why you got "30, SYNTAX ERROR".
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