.TT128 LDA QQ19 \ Set K3 = the x-coordinate of the centre STA K3 LDA QQ19+1 \ Set K4 = the y-coordinate of the centre STA K4 LDX #0 \ Set the high bytes of K3(1 0) and K4(1 0) to 0 STX K4+1 STX K3+1 \STX LSX \ This instruction is commented out in the original \ source INX \ Set LSP = 1 to reset the ball line heap STX LSP LDX #2 \ Set STP = 2, the step size for the circle STX STP JSR CIRCLE2 \ Call CIRCLE2 to draw a circle with the centre at \ (K3(1 0), K4(1 0)) and radius K \LDA #&FF \ These instructions are commented out in the original \STA LSX \ source RTS \ Return from the subroutineName: TT128 [Show more] Type: Subroutine Category: Drawing circles Summary: Draw a circle on a chart Deep dive: Drawing circlesContext: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: This subroutine is called as follows: * TT14 calls TT128

Draw a circle with the centre at (QQ19, QQ19+1) and radius K. Arguments: QQ19 The x-coordinate of the centre of the circle QQ19+1 The y-coordinate of the centre of the circle K The radius of the circle

[X]

Subroutine CIRCLE2 (category: Drawing circles)

Draw a circle (for the planet or chart)

[X]

The ball line heap pointer, which contains the number of the first free byte after the end of the LSX2 and LSY2 heaps (see the deep dive on The ball line heap for details)