VSDD Driver Functions in NSLIB
------------------------------

b7subs.c
--------

	line(x1,y1,x2,y2,ic,bc)
	int x1,y1,x2,y2,ic,bc;

	     line(x1,y1,x2,y2,ic,bc) -- draw a line from (x1,y1) to (x2,y2) if bc==0,
		or a rectangle with corners at (x1,y1) and (x2,y2) in mode ic 

	point(x,y,ic)
	int x,y,ic;

		point(x,y,ic) -- plot a point according to ic

	SetCLT(n,r,g,b)
	int n,r,g,b;

		SetCLT(n,r,g,b) -- Set color lookup table values

nsclip.c
--------

	int
	Clip(x1,y1,x2,y2)
	double x1, y1, x2, y2;

		Clip(x1,y1,x2,y2) -- clip a line and draw its visible portion

		returns 0 if line not visible,  1 if some portion was visible

nsgraf.c
--------

	double	Clipxl,		/* left clipping limit -- world units */
		Clipxr,		/* right clipping limit -- world units */
		Clipyb,		/* bottom clipping limit -- world units */
		Clipyt,		/* top clipping limit -- world units */
		Wxl,		/* window left edge -- world units */
		Wxr,		/* window right edge -- world units */
		Wyb,		/* window bottom edge -- world units */
		Wyt,		/* window top edge -- world units */
		Vxl,		/* viewport left edge -- screen units */
		Vxr,		/* viewport right edge -- screen units */
		Vyb,		/* viewport bottom edge -- screen units */
		Vyt,		/* viewport top edge -- screen units */
		WVxm,		/* windowed view x scale factor */
		WVxa,		/* windowed view x offset */
		WVym,		/* windowed view y scale factor */
		WVya,		/* windowed view y offset */
		Cwx,		/* current x -- world units */
		Cwy;		/* current y -- world units */

	int	PenBgnd,	/* current pen background color for lines */
		PenFgnd,	/* current pen foreground color for lines */
		ChrBgnd,	/* current background color for characters */
		ChrFgnd;	/* current foreground color for characters */

	LineTo(x,y)
	double x, y;

		LineTo(x,y) -- Draw a line from current position to (x,y)

	MoveTo(x,y)
	double x, y;

		MoveTo(x,y) -- Move current position to (x,y)

	NSinit()

		NSinit() -- Initialize NSPAK variables

	int
	SetBgnd(color)
	int color;

		SetBgnd(color) -- set character background color
		Returns old background color.

	int
	SetFgnd(color)
	int color;

		SetFgnd(color) -- set character foreground color
		Returns old foreground color.

	SetPen(bcolor,fcolor)
	int bcolor, fcolor;

		SetPen(bcolor,fcolor) -- set pen colors for lines

	SetView(x1,y1,x2,y2)
	int x1, y1, x2, y2;

		SetView(x1,y1,x2,y2) -- Set viewport edges

	SetWind(x1,y1,x2,y2)
	double x1, y1, x2, y2;

		SetWind(x1,y1,x2,y2) -- Set window edges

	static
	Setwv()

		Setwv() -- Setup window to viewport transformation

	ShowLine(x1,y1,x2,y2)
	double x1, y1, x2, y2;

		ShowLine(x1,y1,x2,y2) -- Draw a line between (x1,y1)-(x2,y2)

	VPbord()

		VPbord() -- outline viewport

	WctoSc(x,y,sx,sy)
	double x, y;
	int *sx, *sy;

		WctoSc(x,y,sx,sy) -- Convert world coordinates to screen coordinates

nslseg.c
--------

	static int
	abs(a)
	int a;

        	i = abs(a) -- return absolute value of a

	int
	lseg(x1,y1,x2,y2,t)
	int x1,y1,x2,y2,t;

		lseg(x1,y1,x2,y2,t) -- draw a line from (x1,y1) to (x2,y2) in mode t

	static int
	sign(a)
	int a;

		i = sign(a) -- return sign of a as -1, 0 , or 1