| 10 REM "Caculate the mandelbrot set" | |
| 20 REM "The iteration cutoff, threshold, and resolution" | |
| 30 N=24 | |
| 40 T=4 | |
| 50 R=100 | |
| 100 C0=0: C1=0 | |
| 110 CLS | |
| 200 REM "walk through the grid" | |
| 210 FOR J=2*R+1 TO 1 STEP -1 | |
| 220 FOR I=1 TO 3*R+1 | |
| 230 C0=-2+(I-1)/R: C1=-1+(J-1)/R | |
| 240 GOSUB 4000 | |
| 250 GOSUB 5000 | |
| 280 NEXT | |
| 300 NEXT | |
| 310 FOR I=1 TO 12: PUT 27, "B": NEXT | |
| 999 END | |
| 4000 REM "do an iteration on c" | |
| 4010 Z0=C0: Z1=C1 | |
| 4020 FOR K=1 TO N | |
| 4030 S0=Z0*Z0: S1=Z1*Z1 | |
| 4040 IF S0+S1>T THEN BREAK | |
| 4050 X0=S0-S1+C0 | |
| 4060 X1=2*Z0*Z1+C1 | |
| 4070 Z0=X0: Z1=X1 | |
| 4080 NEXT | |
| 4090 RETURN | |
| 5000 REM "plot a point" | |
| 5010 IF K>N: COLOR 0: PLOT I,J: RETURN | |
| 5020 COLOR 255-INT(K/N*255) | |
| 5030 PLOT I,J | |
| 5040 RETURN | |