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2022-08-26
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PEEKs, POKEs, & SYSes - Part 8
------------------------------
======================================
Location: 16 Hexadecimal: $0010
Official Label: SUBFLG Type: RAM
Useful BASIC commands: PEEK, POKE
There are 2 cases in which a vari-
able name might be followed immedi-
ately by a number in parentheses. One
of these is an array reference 'A(5)',
and the other is a defined-function
reference 'DEF FNA(5)'. Since integer
variables are illegal as dummy argu-
ments to a defined-function, this flag
is used to distinguish the two so that
BASIC knows if integers are allowed!
======================================
Location: 17 Hexadecimal: $0011
Official Label: INPFLG Type: RAM
Useful BASIC commands: PEEK, POKE
In case you hadn't noticed, the
format of data in a DATA statement is
identical to the format of data to be
entered via an INPUT statement. BASIC
uses the same routine for both, and
part of that routine for GET as well.
So, this location contains a 0 for IN-
PUT, a 64 ($40) for GET, and a 152
($98) for READ (to read DATA state-
ments). That way, the routine knows
how to handle the subtle differences
between READ and INPUT (such as where
to get the data!).
======================================
Location: 18 Hexidecimal: $0012
Official Label: TANSGN Type: RAM
Useful BASIC commands: PEEK, POKE
This flag has 2 purposes. BASIC
uses it to keep track of the sign of
the result of trig (SIN, COS & TAN)
functions during computation, and as a
place to hold the result of a compari-
son (255 (-1, $FF) for '<', 0 for '=',
1 for '>').
======================================
Location: 19 Hexadecimal: $0013
Official Label: (none) Type: RAM
Useful BASIC commands: PEEK, POKE
It's a shame that Commodore didn't
supply this one with its own label!
It holds the logical file # currently
being used for input. Normally, this
is zero. The file # here is used for
only one thing: to check to see if
INPUT needs to output a '?' prompt be-
fore asking for the INPUT, and whether
to output a RETURN after the INPUT is
entered. If this location is zero,
the prompts are output. If non-zero,
they aren't! If you would like to
prevent the '?' on INPUT's, you don't
need to open the keyboard as a file.
Just POKE 19,1. You will have to
print your own RETURN's after each IN-
PUT, though! POKE 19,0 to return IN-
PUT to normal.
============End of Article============