	This utility produces a graph with contour lines.

	For input you give it grid of z values in a file the 
 	x and y values are assumed.

	e.g. a 4x3 grid of points would look like this:
--- cut here ----
! nx 4 ny 3 xmin 0 xmax 0 xmax 6 ymax 0 ymax 10
1 1 1 1
1 2 2 1
1 1 1 1
---- and here ---

This defines the points		0,0,1   2,0,1   4,0,1  6,0,1
				0,5,1   2,5,2   4,5,2  6,5,1
				0,10,1  2,10,1  4,10,1 6,10,1
	
	You would normally generate this file using the utility LETZ
	or FITZ.

	LETZ takes an x,y function and produces a grid of z values

	FITZ takes a file of x,y,z data points and fits a grid of z values.

	Having created a data file of the correct sort CONTOUR will
	ask for a list of values to contour at,  you can enter 
	a list of values, e.g. "1 2 3 4.5 5"  or you can enter
	a range and step size e.g. "1:3:.5" which would generate
	"1 1.5 2 2.5 3"

	You are then asked if you want the lines labeled with 
	the letters A...Z or by the actual numbers.

	Then you are asked for a file name to write output to.  If
	you give the name XYZ then CONTOUR will create:

		xyz.gle		! The gle file to draw the contour plot
		xyz.dat		! The data file containing the contour lines
		xyz.lab		! A gle include file which labels the graph
		xyz.key		! A gle include file which draws a key

	Then wait while the contours are calculated, this takes some
	time (even on a fast PC) e.g. 10 seconds on 33Mhz 386.    
	The exact time will depend on the number of points and number
	of contour lines you are using.

                     