DECLARE SUB plane ()
DIM X(9000)
DIM Y(9000)
DIM A(9000)
DIM B(9000)

i = 1
1
X = -500
Y = -500
CLS
SCREEN 9
WINDOW (-160 / i, -100 / i)-(160 / i, 100 / i)

'<--->NUMBER PLANE<--->`

LINE (-160, -100)-(160, 90), 14, B

LINE (0, -450)-(0, 450), 14
LINE (-450, 0)-(555, 0), 14
FOR i = -500 TO 170 STEP 10
LINE (i, -2)-(i, 2), 14
LINE (-2, i)-(2, i), 14


NEXT i
LINE (-160, 91)-(161, 100), 0, BF

'<--->NUMBER PLANE<--->`
D = 9.5
FOR X = -D TO D STEP .01

Y = X ^ 2

'LINE (A, B)-(X, Y), 1
'A = X
'B = Y
PSET (X, Y)

NEXT X





LOCATE 25, 1
zoom:
INPUT i
IF i = 0 THEN i = 1



GOTO 1

SUB plane


END SUB