CALL OOPEN('DSK','PLOT')
	DO 80 N = 1,51,5
	R = FLOAT(N-1) / 100.0
	IX = IFIX(R+100.5) - 100
	X = R - FLOAT(IX)
	IF (IREM(IX/2)) 10,20,10
10	X = -X
20	JX1 = IFIX(180.0*X + 90.5)
	JY1 = 99
	CALL WPLOT(0,0,0)
	CALL WPLOT(180,0,1)
	CALL WPLOT(180,198,1)
	CALL WPLOT(0,198,1)
	CALL WPLOT(0,0,1)
	CALL WPLOT(JX1,JY1,0)
	DO 70 I = 1,N
	THETA = 2.0*3.141593*FLOAT(I) / FLOAT(N)
	X = R * COS(THETA)
	Y = R * SIN(THETA)
	IX = IFIX(X+100.5) - 100
	IY = IFIX(Y+100.5) - 100
	X = X - FLOAT(IX)
	Y = Y - FLOAT(IY)
	IF (IREM(IX/2)) 30,40,30
30	X = -X
40	IF (IREM(IY/2)) 50,60,50
50	Y = -Y
60	JX2 = IFIX(180.0*X + 90.5)
	JY2 = IFIX(198.0*Y + 99.5)
	CALL WPLOT(JX2,JY2,1)
70	CONTINUE
	CALL WPLOT(0,0,-1)
80	CONTINUE
	CALL OCLOSE
	CALL CHAIN('PLOT')
	END