10 CLS: PI = 3.14159
20 SCREEN 9
30 INPUT "Numero delle lunghezze d'onda: ", N
40 IF N < 3 OR N > 20 OR N <> INT(N) THEN CLS: GOTO 30
50 INPUT "Colore dell'onda: ", COL
60 IF COL < 9 OR COL > 14 OR COL <> INT(COL) THEN CLS: GOTO 50
70 WINDOW (-4, -3)-(4, 3)
80 FOR THETA = 0 TO 2 * PI STEP .006
90 C = COS(THETA)
100 S = SIN(THETA)
110 S1 = .3 * SIN(N * THETA) + 1
120 X = -1.5 * S * S1
130 Y = 1.5 * C * S1
140 PSET (X, Y), COL
150 NEXT THETA
160 LINE (-4, 0)-(4, 0), 15
170 LINE (0, -3)-(0, 3), 15
180 A$ = INKEY$: IF A$ = "" THEN 180
190 CLS: SYSTEM