This set of program packages was the result of a concerted effort
to produce a PORTABLE set of graphic procedures which could be easily
transported from one machine to another. It was produced by myself and
a colleague .. Jack Gilmer.

	The problem originated because we had access to a number of
computers ranging from a large mainframe where we work ( at a university)
through several minis to the micros we have at home. There are many
different graphical packages available to us but it was all too
confusing to keep straight - life is just too short to become adept in
such a variety of programs. Secondly, most graphical packages are very
generalized and really are not well adapted to the type of work we do.
As physical scientists, we mostly wanted procedures which were well
suited to plotting line graphs - we essentially NEVER use bar plots,
pie plots etc.

	So, we designed a number of procedures which would fulfill our
requirements. The philosophy was to write the desired user oriented
procedures in terms of simpler procedures which ultimately call a very few
very primitive procedures which can be modified easily for any particular
combination of computer and plotter.

	The first set of these was written by me using Apple UCSD Pascal
with its 'Turtlegraphics' procedures for CRT graphics and a Houston
Instruments 'HIPLOT' plotter. Later, Jack adapted the packages to an LSI-11
using Whitesmith's Pascal. This was done for two plotting systems; one of
these was an ADM3+ CRT plus a Digital Engineering 'Graphx' hard copy unit.
The other was for a HP 7225A pen plotter.

	The packages on this diskette are the latter two which have been
copied from the DEC diskettes using a program on the MTPUG program disk #1.
That program has, incidentally, been a godsend.

	If you want to use these procedures, you will have to adapt the
package to your machine/plotter combination by rewriting the serial I/O
outines and the primitive procedures called;

	PENUP
	PENDOWN
	DRAWTO

I have modified the ADM3 package slightly so that it will at least compile
under Pascal MT+. The other one, called GRHP.SRC is just as it was on the
LSI-11. You will have to modify it a bit more extensively since Whitesmith's
Pascal does not have the UCSD string data type we have in MT+ but uses ZERO
terminated strings instead.

	Incidentally, since these procedures were all originally written
using UCSD Pascal, the more primitive procedures could all be hidden from
the user and so I used procedure names which were fairly descriptive. In
Pascal MT+, you may want to change the names to something more unusual for
these procedures in order not to give other procedures in your program the
same name.

	The plotted data is specified by a number of pre-defined data types
which are listed below. All plots were to be in absolute coordinates with
values given in MILLIMETERS.

	The data types are:

    astringtype = STRING[132];      

    aendtype = (noend, point, square, triangle, cross, ecks, diamond,
                circle);

    alinetype = (noline, solid, dotted, dashed, dotdashed, 
                 dotdotdashed);

    apointtype =  RECORD	(* absolute position in millimeters *)
                    x,
		    y:  REAL;
		  END;

	You can see that we were primarily concerned with scientific type
plots since we wanted to be able to specify the type of line plotted and the
type of end to that line. For example, to plot a number of data points as
triangles, you use a particular procedure to set the type of line to 'noline'
and the type of endpoint to 'triangle'. Then you just call the plotting
procedure with the x,y positions of the points.

	The procedures and functions which you will use in your program are:

	AINIT - this initializes the plotter ( if it needs it ) to the
		lower left corner.

	AWINDOW - this sets the plotting window. Lines which are called to
		be plotted and which extend outside this window are cut off
		at the boundaries by the software.

	ADEFAULT - sets the default parameters such as the pattern size for
		patterned lines (dotted, dashed etc), the endpoint sizes etc.

	ABADCALL - a function to determine whether or not the called for point
		is so far outside the plotting window that serious arithmetic
		round off errors will cause plotting errors. This function
		has not been implemented in any of the packages we've written.
		This probably means that it is not necessary.

	AMAKECOPY - sets the hard copy unit into motion if it is different
		from the CRT display.

	ASETWINDOW - sets up the window limits.

	ASETPLOT - sets up the plotting parameters. These are the type of
		line, the type of endpoint etc.

	APLOT - plots a line to the point specified. The characteristics of
		the line and its end are what has last been set with
		ASETPLOT.

	ASETSTR - sets up the characteristics of the text plotting. These
		are the character size, character orientation, character
		spacing, string orientation and character width. For many
		plotters like the ADM3+ plus Graphx combination, this
		procedure does nothing since the text characteristics are
		fixed.

	ASTR - writes a string starting in the current pen location.

	ATEXT - switches back from graphical to text mode ( needed for
		all types of CRT monitors).

	AGRAPH - switches to graph mode

	AWHERE - returns the current pen position.


	Good luck... I would be interested in hearing from anyone who uses
these packages for another computer/plotter combination. I would be glad to
help out anyone who is having difficulty in transporting these procedures
to another system - just please don't expect me to rewrite the whole thing.
Jack and I would also be interested in hearing from anyone who has construct-
ive comments about the utility of the procedures and suggestions for
improvements.

	J.A. Koehler
	2 Sullivan St.
	Saskatoon, SK, S7H-3G8              28 October, 1982