Your Commodore - Commodore Is Awesome

next pointer simply moves on to the
next character.
Parameters
Having sorted out the separators, we
want to evaluate the parameters. This is
readily achieved by calling SAD8A.
This evaluates the expression which is
being pointed at by the text pointer
and stores the result in FAC/1.
Consider the Listing L
JSR SAEFD
20 JSR MINA
This will extract a single parameter
after checking for a comma and leave
the result in FAC/1. In other words, it
checks the syntax:
SYS address, parameter
This sytem is in fact quite tolerant.
Spaces are ignored allowing freedom
of syntax. The parameter can be any
valid expression or a numeric value.
Listing 2 is more complex. It
checks for a rather bizarre syntax ie.
SYS address,(parameter 1),parameter
2
You will note that I've used the
routine at $1371
7parametes
in FAC/1 to integers.
7 You t o may, alternatively, wish to
ctransfer o n non-numeric v e r data in strings.
t
Again, there are routines for this
purpose. First, we call SAD9E to
t
evaluate
h
the
e
expression. This time. the
routine will detect that we have a string
and will exit with the length of the
string in the accumulator and the start
address of the string in S64 and $65. A
call to $B6A6 erases any previous cop
of the string by moving the string
pointers. On leaving this routine, the
start address of the string is in $22/$23.
Listing 3 handles the syntax:
SYS address, string
I LISTING 3
MACHINE CODE
This routine will accept text or
strings. e.g.
SYS address,AS
SYS address„
—
text" The date given by Listing 3 can be
easily manipulated. Listing 4 takes this
data and moves it to a buffer.
I LISTING 4
10 LDY #0
20 LOOP LDA STRINGADD ,
30 STA BUFFER,Y
40 INY
50 CPY STRINGLEN
60 BNE LOOP OP
So what happens if you want to
input numeric information during the
operation of the program? Well we can
use some of the techniques described
earlier in this series. Consider listing 5.
20
30
GETSTR JSR $AEFD
JSR $AD9E
;
;
CHECK COMMA
EVAL EXPRESSION
40 JSR $B6A6 ; SAVE ADDRESS IN $22/$23
50 STA STRINGLEN ; SAVE STRING LENGTH
60
70
80
90
95
LDA $22
STA STRINGADD
LDA $23
STA STRINGADD+1
RTS
;
;
;
;
START ADDREESS OF
STRING — LSB
START ADDRESS OF
STRING — MSB
I
40 L BUFFER = $0200
40 I CHKSTR = $AD8A
S70
LDY #0
T80
LOOP JSR $FFCF
I
90 CMP #13
100
N BEQ QUIT
110 STA
G
BUFFER,Y
120 INY
5
130 JMP LOOP
;
;
;
;
;
;
INPUT ROUTINE
IF RETURN EXIT
PUT INTO BASIC
INPUT BUFFER
140
150
160
170
180
OUT
STA
LDA
STA
LDA
LDA #0
BUFFER,Y
#