JOY

VIC-20 C64 C16 Plus/4 C128 X16 M65

The JOY() function returns the status of either joysticks.

DECLARE FUNCTION JOY AS BYTE (portnum AS BYTE) SHARED STATIC INLINE

Where portnum is an expression that evaluates to 1 or 2.

The return value is a BYTE where bits corresponding to a direction are set or unset. The direction to bit mapping if different on each target:

• On C64 C128 M65:
  • Bit #0 is set if joystick is being pulled up
  • Bit #1 is set if joystick is being pulled down
  • Bit #2 is set if joystick is being pulled left
  • Bit #3 is set if joystick is being pulled right
  • Bit #4 is set if fire button is depressed
• On VIC-20:
  • Bit #2 is set if joystick is being pulled up
  • Bit #3 is set if joystick is being pulled down
  • Bit #4 is set if joystick is being pulled left
  • Bit #5 is set if fire button is depressed
  • Bit #7 is set if joystick is being pulled right
• On C16 and Plus/4:
  • Bit #0 is set if joystick is being pulled up
  • Bit #1 is set if joystick is being pulled down
  • Bit #2 is set if joystick is being pulled left
  • Bit #3 is set if joystick is being pulled right
  • Bit #6 is set if fire button is depressed on joystick 1
  • Bit #7 is set if fire button is depressed on joystick 2

Using the following example, you can read the joystick status on all platforms:

' Uncomment if target is VIC-20
'CONST JOYUP = 4
'CONST JOYDN = 8
'CONST JOYLT = 16
'CONST JOYRT = 128
'CONST J1FIRE = 32

' Uncomment if target is C64
'CONST JOYUP  = 1
'CONST JOYDN  = 2
'CONST JOYLT  = 4
'CONST JOYRT  = 8
'CONST J1FIRE = 16
'CONST J2FIRE = 16

' Uncomment if target is C16 or C Plus/4
'CONST JOYUP  = 1
'CONST JOYDN  = 2
'CONST JOYLT  = 4
'CONST JOYRT  = 8
'CONST J1FIRE = 64
'CONST J2FIRE = 128

DIM j AS BYTE
lab:
  j = JOY(1)
  IF j = 0 THEN GOTO lab
  IF j AND JOYUP THEN PRINT " up";
  IF j AND JOYDN THEN PRINT " down";
  IF j AND JOYLT THEN PRINT " left";
  IF j AND JOYRT THEN PRINT " right";
  IF j AND J1FIRE THEN PRINT " fire";
  PRINT ""
  GOTO lab