DEFB	+31,duplicate	X0+X, Y0+Y, Xn+1, Xn+1
		DEFB	+38,end-calc	Next Xn', the approximate
				value of Xn reached by
				the line-drawing subroutine
		LD	A,(COORDS-lo)	is copied to A
		CALL	2D28,STACK-A	and hence to the stack.
		RST	0028,FP-CALC	X0+X,Y0+Y,Xn+1,Xn'
		DEFB	+03,subtract	X0+X,Y0+Y,Xn+1,Xn+1,Xn'
				- Xn' = Un'
		DEFB	+E0,get-mem-0	X0+X,Y0+Y,Xn+1,Un',Yn
		DEFB	+E2,get-mem-2	X0+X,Y0+Y,Xn+1,Un',Yn,Vn
		DEFB	+0F,addition	X0+X,Y0+Y,Xn+1,Un',Yn +
				Vn = Yn+1
		DEFB	+C0,st-mem-0	(Yn+1 is copied to mem-0).
		DEFB	+01,exchange	X0+X,Y0+Y,Xn+1,Yn+1,Un'
		DEFB	+E0,get-mem-0	X0+X,Y0+Y,Xn+1,Yn+1,
				Un',Yn+1
		DEFB	+38,end-calc
		LD	A,(COORDS-hi)	Yn', approximate like Xn', is
		CALL	2D28,STACK-A	copied to A and hence to the
				stack.
		RST	0028,FP-CALC	X0+X,Y0+Y,Xn+1,Yn+1,
				Un',Yn+1,Yn'
		DEFB	+03,subtract	X0+X,Y0+Y,Xn+1,Yn+1,
				Un',Vn'
		DEFB	+38,end-calc
		CALL	24B7,DRAW-LINE	The next 'arc' is drawn.
		POP	BC	The arc-counter is restored.
		DJNZ	2425,ARC-LOOP	Jump if more arcs to draw.
245F	ARC-END	RST	0028,FP-CALC	The co-ordinates of the end
		DEFB	+02,delete	of the last arc that was drawn
		DEFB	+02,delete	are now deleted from the stack.
		DEFB	+01,exchange	Y0+Y, X0+X
		DEFB	+38,end-calc
		LD	A,(COORDS-lo)	The X-co-ordinate of the end of
		CALL	2D28,STACK-A	the last arc that was drawn, say
		RST	0028,FP-CALC	Xz', is copied to the stack.
		DEFB	+03,subtract	Y0+Y, X0+X - Xz'
		DEFB	+01,exchange	X0+X - Xz', Y0+Y
		DEFB	+38,end-calc
		LD	A,(COORDS-hi)	The Y-co-ordinate is obtained.
		CALL	2D28,STACK-A
		RST	0028,FP-CALC	X0+X - Xz', Y0+Y, Yz'
		DEFB	+03,subtract	X0+X - Xz', Y0+Y - Yz'
		DEFB	+38,end-calc
2477	LINE-DRAW	CALL	24B7,DRAW-LINE	The final arc is drawn to reach
				X0+X, Y0+Y (or close the
				circle).
		JP	0D4D,TEMPS	Exit, setting temporary colours.

THE 'INITIAL PARAMETERS' SUBROUTINE
This subroutine is called by both CIRCLE and DRAW to set their initial parameters. It is called by CIRCLE with X, Y and the radius Z on the top of the stack, reading upwards. It is called by DRAW with its own X, Y, SIN (G/2) and Z, as defined in DRAW i. above, on the top of the stack. In what follows the stack is only shown from Z upwards.
The subroutine returns in B the arc-count A as explained in both CIRCLE and DRAW above, and in mem-0 to mem-5 the quantities G/A, SIN (G/2*A), 0, COS (G/A), SIN (G/A) and G. For a circle, G must be taken to be equal to 2*PI.

247D	CD-PRMS1	RST	0028,FP-CALC	Z
		DEFB	+31,duplicate	Z, Z
		DEFB	+28,sqr	Z, SQR Z
		DEFB	+34,stk-data	Z, SQR Z, 2