!MANDELBROT PROGRAM: BOUNDARY SCAN

SET MODE "graphics"

ASK PIXELS hpix,vpix

LET ratio=hpix/vpix

SET WINDOW -2,2,-2/ratio,2/ratio

DIM JK(-301 TO 301,-301 TO 301)

!Creates a big matrix of about 600x600 to store the results of the iteration for the points (j,k) in the c-plane

!By default, all elements of JK are initially zero.

FOR j=-300 to 300

FOR k = -300 to 300

LET x = 0

LET y = 0

FOR n=1 to 200

LET x1 = x*x - y*y + j/150

LET y1 = 2*x*y + k/150

LET rsq = x1*x1 + y1*y1

IF rsq>4 THEN EXIT FOR

LET x = x1

LET y = y1

NEXT n

IF n>200 THEN LET JK(j,k)=1

!NOTE: JK=0 except at the points belonging to the M-set, where JK=1.

NEXT k

NEXT j

FOR j=-300 to 300

FOR k = -300 to 300

IF JK(j,k)=1 AND (JK(j+1,k)=0 OR JK(j-1,k)=0 OR JK(j,k+1)=0 OR JK(j,k-1)=0) THEN PLOT j/150,k/150

!NOTE: Boundary Plot : it only plots those points on the M-set which have at least one neighbor not on the M-set

NEXT k

NEXT j

END