Program listing

DEFINT A-Z				'integers are faster
DECLARE SUB Init			'Allows switching on cells
DECLARE SUB Go ()			'Allows switching on cells
DECLARE SUB Edge			'Draws edge cells
DIM SHARED L(47, 34), T(47, 34)		'Life/Temp cell arrays
DIM SHARED E(17), count			'life/death array & count
start: CLEAR				'null all arrays for restarts
E(3) = 1: E(11) = 1: E(12) = 1 		'3 neighbours give life to
	'dead cell, 2 or 3 keep live cell (value=9) alive.
	'All other E() stay equal to 0 and kill cell.
Init
Go
GOTO start
END

SUB Edge
FOR r = 1 TO 33
 IF L(0, r) = 1 THEN LINE (1, r * 10 + 1)-STEP(10, 7), 1, BF
 IF L(47, r) = 1 THEN LINE (612, r*10 +1)-STEP(10, 7), 1, BF
NEXT
FOR c = 0 to 47
  IF L(c, 0) = 1 THEN LINE (c * 13 + 1, 1)-STEP(10, 7), 1, BF
  IF L(c, 34) = 1 THEN LINE (c*13 +1, 341)-STEP(10, 7), 1, BF
NEXT
PRINT "	Esc to quit. Any other key to pause and restart."
count = count + 1: PRINT count
END SUB

SUB Go
DO
  SCREEN 9, , 1, 0: CLS  		'display page 0, draw on page 1
  Edge					'draw any live edge cells & message
  FOR r = 1 TO 33: FOR c = 1 TO 46 	'edge cells not changed
   ru = r - 1: rd = r + 1: cl = c - 1: cr = c + 1
   'Count "live" cells adjacent. Add 9 if cell itself alive.
   's can have any value 0-8 if cell dead, 9-17 if cell alive
   s = L(cl, rd) + L(cl, r) + L(cl, ru) + L(c, rd) + L(c, ru)
   s = s + L(cr, rd) + L(cr, r) + L(cr, ru) + 9 * L(c, r)
   T(c, r) = E(s) 'set life/death of T()using fixed array E()
   x = c * 13 + 1: y = r * 10 + 1
   IF T(c, r) = 1 THEN LINE (x, y)-STEP(10, 7), 1, BF
  NEXT: NEXT
 'routine, m$ = INKEY$: IF m$ > °" to END IF, here if desired
  SCREEN 9, , 0, 1: CLS
 'switch pages & use T() to calc L() Edge
  FOR r = 1 TO 33: FOR c = 1 TO 46
   ru = r - 1: rd = r + 1: cl = c - l: cr = c + 1
   s = T(cl, rd) + T(cl, r) + T(cl, ru) + T(c, rd) + T(c, ru)
   s = s + T(cr, rd) + T(cr, r) + T(cr, ru) + 9 * T(c, r)
   L (c, r) = E (s) : x = c * 13 + 1: y = r * 10 + 1
   IF L(c, r) = 1 THEN LINE (x, y)-STEP(10, 7), 1, BF
  NEXT: NEXT
  m$ = INKEY$
  IF m$ > "" THEN			'if key
   SELECT CASE m$
    CASE CHR$(27): CLS : EXIT DO	'escape
    CASE ELSE: DO: LOOP WHILE INKEY$	'pause for key
   END SELECT
  END IF
LOOP					'keep going
END SUB

SUB Init
SCREEN 9, , 0, 0'EGA 640 X 350. Use 48 cells across, 35 down
LINE (13, 10)-STEP(598, 330), 4, B 'cells outside are stable
PRINT "Cursors. Space toggles life. ENTER starts. Esc ends"
c = 24: r = 17				'initial column, row
D0					'outer loop
 x = c * 13: y = r * 10			'cells 13 X 10 pix.
 DO					'flash cell border
  IF TIMER > RefTime! THEN		'check if .3 sees up
  RefTime! = TIMER + .3: col = 1 - col	'colour flips 0/1/0
  LINE (x, y)-STEP(12, 9), Col, B	'draw border
 END IF
 c$ = INKEY$				'check keystroke
LOOP WHILE c$ _ ""
LINE (x, y)-STEP(12, 9), 0, B		'check keystroke
SELECT CASE c$				'obey key
  CASE CHR$(27): END			'Escape
  CASE CHR$(13): EXIT SUB		'Enter starts `Go'
  CASE CHR$(32): L(c, r) = 1 - L(c, r)	'Spacebar flips cell
   LINE (x + 1, y + 1)-STEP(10, 7), L(c	'fill cell
   T(c, r) = L(c, r)		'edge cells need T() = L()
  CASE CHR$(0) + CHR$(75): c = (c + 47) MOD 48	'left
  CASE CHR$(0) + CHR$(77): c = (c + 1) MOD 48	'right
  CASE CHR$(0) + CHR$(72): r = (r + 34) MOD 35	'up
  CASE CHR$(0) + CHR$(80): r = (r + 1) MOD 35	'down
  CASE ELSE 'do nothing
 END SELECT 'modular arithmetic handles screen edge problem
LOOP
END SUB