DEF Fnf(x,z) Fnf=500000#/(9.999999999999999D-12+x*x+z*z) END DEF SCREEN 2 WINDOW(-160,-100)-(160,100) DIM vz(-20 TO 20)AS INTEGER FOR x=-160 TO 160 STEP 5 FOR z=-100 TO 100 y=Fnf(x,z) IF y<>0 THEN vz(z\5)=-1 rx=x*.99^y ry=z*.99^y IF z=-100 THEN PSET(rx,ry)ELSE LINE-(rx,ry) NEXT NEXT FOR z=-100 TO 100 STEP 5 IF vz(z\5)THEN FOR x=-160 TO 160 y=Fnf(x,z) rx=x*.99^y ry=z*.99^y IF x=-160 THEN PSET(rx,ry)ELSE LINE-(rx,ry) NEXT ELSE LINE(-160,z)-(160,z) END IF NEXT