MachiKania Type M sample BASIC program / Mandelblot https://rosettacode.org/wiki/Mandelbrot_set#Processing

MANDEL.BAS

USEGRAPHIC 5
W=288
H=216
I=0
J=0
F=10
X=W/4
Y=H/8
V=2
Z=1

K=0
L=0

FOR K=0 TO W
  T#=(FLOAT#(K)+FLOAT#(I))/FLOAT#(X)-FLOAT#(V)
  FOR L=0 TO H
    U#=FLOAT#(Z)-(FLOAT#(L)+FLOAT#(J))/FLOAT#(W)
    R#=0
    S#=0
    P#=0
    Q#=0
    N=1
    WHILE (P#+Q#)<4
      IF N>255 THEN BREAK
      Q#=S#*S#
      P#=R#*R#
      S#=2*S#*R#+U#
      R#=P#-Q#+T#
      N=N+1
    WEND
    PSET K,L,N
  NEXT
NEXT

END