Commodore VIC-20 User Manual page 183

Chapter 5: Game Controllers
169
63010
63020
63030
63040
Checks to see if any key is pressed.
63050
63060
If not, RETURNs, leaving all variables set to zero.
These lines form a loop to scan the key table for
the key that was pressed. A FOR-NEXT loop is not used,
since we want to RETURN immediately if the key is found.
(Remember that you must always terminate a FOR loop
with a NEXT, and we want to stop this loop as soon as
possible.)
Checks for the Fire button.
RETURNs to main program.
USING THE KEYBOARD JOYSTICK
Your program should be entered ahead of statement 62000. You can
SA VE a copy of these routines by themselves to use as a base on which to
build programs.
To see what can be done with the "keyboard joystick" routines, try
using them with the demonstratidn program below.
19 GOSUB 62000
20 A'(0)·" lEFT":A.Cl)II" ":AS(2)."RIGHT"
30 BS(0)="DOWN ":BS(l)=" ":BS(2)="UP"
40 C'(0)."FIRE":C'(1)="IFIRE!!"
50 POKE
6501
128
1013 PRINT":'}"
110 PRINT"." , ; A'(XI+1)
i
"I";
1'(YI+1);
Spe(,);
C$(FB)
1213 GOSUB63000
1313 GOT0110
62090 REM KEY TABLE VALUES
62109 DATA IIOlll"."I"I"IM,J,U
622130 REM X INCREMENT VALUES
62399 DATA
9111111101-1/-1/-1
62400 REM Y INCREMENT VALUES
62500 DATA 1,1101-1/-11-1,911
626013 FOR 1=0 TO 7: READ KT'(I): NEXT
62700 FOR 1=0 TO 7: READ XT(I): NEXT
62900 FOR 1=0 TO 7: READ YTCI): NEXT
63900 XI=0: YI=e: FI=S: lI=0
63019 GET KE'
63020 IF KE$ .. "" THEN RETURN
63030 IF K' .. K'(lI) THENYI • Y(ll): XI II XT(LI): RETURN
63040 LI .. LI+l: IF LI
<
8 THEN 630313
63058 IF KE. .. "K" THEN FB • 1
63a6e RETURN