NEW
100 REM PROGRAM TO DRAW MANDLEBROT SET
110 REM P. MAINWARING, MARCH 19TH 1990
120 *TV 255,1
130 ITERS=32
140 SCALE=1
150 XRANGE=-2.5
160 YRANGE=-1.5
170 DIM A(3),B(3)
180 FOR I=0 TO 3
190 READ A(I),B(I)
200 NEXT I
210 DATA 0,0,1,1,0,1,1,0
220 MODE 1
230 XSTP=4
240 YSTP=4
250 COLS=4
260 MAXX=1280/XSTP
270 MAXY=1024/YSTP
280 VDU 23;8202;0;0;0;
290 FOR I=0 TO 3
300 FOR J=A(I) TO MAXY/SCALE STEP 2
310 FOR K=B(I) TO MAXX/SCALE STEP 2
320 CR=XRANGE+K*4/(MAXX/SCALE)
330 CI=YRANGE+J*3/(MAXY/SCALE)
340 ZM=0:ZR=0:ZI=0:ZR2=0:ZI2=0
350 IT=0
360 REPEAT
370 Z1=ZR2-ZI2+CR
380 Z2=2*ZR*ZI+CI
390 ZR=Z1
400 ZI=Z2
410 ZR2=ZR*ZR
420 ZI2=ZI*ZI
430 ZM=ZR2+ZI2
440 IT=IT+1
450 UNTIL IT=ITERS OR ZM>=4
460 X%=K*XSTP:Y%=1023-J*YSTP
470 PRINT TAB(0,0);RIGHT$("000"+STR$(X%),4);
480 PRINT ","+RIGHT$("000"+STR$(Y%),4)+")";
490 GCOL 0,COLS-1-INT(IT/(ITERS/(COLS-1))):PLOT 69,X%,Y%
500 NEXT K
510 NEXT J
530 NEXT I
999 END
RUN