100 '           programma 9     PARABOOLSTELSEL
110 CLEAR ,19202 : SCREEN 105,,3,3
120 DEF FNX(X)=INT(1.55*(50+X)+.5)
130 CLS: KEY OFF
140 U=160 : V=160 : H=.5
150 FOR K= -160 TO 160 STEP 20
160     X=-160: Y=-K*X*X/15000+K
170     X1=INT(U+X+H) : Y1=INT(V-Y+H)
180     FOR X=-150 TO 160 STEP 10
190         Y=-K*X*X/15000+K
200		  X2=INT(U+X+H) : Y2=INT(V-Y+H)
210		  LINE (FNX(X1),Y1)-(FNX(X2),Y2),1
220		  X1=X2 : Y1=Y2
230	   NEXT X
240 NEXT K
250 LINE (FNX(0),0)-(FNX(320),320),1,B
260 A$=INKEY$: IF A$="" THEN 260
270 CLS: KEY ON: END
