 
 	The user of BASIC IAS/RSX may wish to produce formatted plots on a
 Tektronix 4014 terminal.  To do this, one may either incorporate the plotting
 subroutines(LB1:[377,377]PLOTIO.BAS) into the user's program(if it is short
 enough), CHAIN to PLOTIO.BAS (giving it a line number to return to), or
 create a plot file with one program and plot it out using the Utility Program
 GRAPH.BAS(on LB:[377,377]).
     GRAPH.BAS is an interactive program capable of displaying up to 10 plots
 at a time on a 4014 terminal.    Commands are of two types, the immediate 
 execution command which either sets up the plot common area or starts the
 plot going, or the 'special' command which does not execute until the
 plot is completed.  The special commands are COPY, PAGE, and HALT.
 Each of these commands waits until the current plot is executing
 before it executes. Before GRAPH starts plotting it erases the terminal
 screen.  It also erases the screen before returning to command input mode
 (after a plot is done).  Hence, if one wishes to get a copy, one had best
 use the copy command.
     Additional HELP may be obtained by typing HELP BASIC GRAPH keyword,
 where keyword is one of
	CREATE		Create a plot file for GRAPH
	COMMANDS	The GRAPH interpreter command list.
 
3	CREATE
     The plot file is created as a virtual array file with the commands
			DIM #n, C(1019)
			OPEN "filespecifier" as FILE #n
 within one's BASIC program.  For detailed information on plot file format
 type HELP BASIC PLOT,
3	COMMANDS
	ADD		ADD data to data set
	BYE		Logoff from BASIC
	CHAIN prog	CHAIN to another BASIC program
	CLOSE		Declare the open data set closed
	COPY		Make Hard Copy when done.(special command)
	DATA		Declare the name of the data set(plot file)
	DELETE		Delete Points from the data set
	HALT		Stops the program after the most recent plot(for debugging)
	OPEN		Declare the data set number in use
	PAGE		Erase screen(special command)
	PLOT		Stop accepting commands, go execute plot
	POINT		Set the type of point plot.
	LINE		Set the type of line plot.
	LIST		List out the data in the plot file
	RUN prog	Run another BASIC program
	STOP		Stop running GRAPH and return to BASIC monitor
	TITLE		Set X and Y titles
	VIEWPORT	Set the data and axis ranges
	WINDOW		Set the area of the terminal screen to plot on
	
 For further HELP on any of the above commands type 
             HELP BASIC GRAPH 'commandname'
 where 'commandname' is any of the above names.
3	OPEN
	OPEN (n)
     From 1 to 10 plot files may be plotted at a time.  The OPEN command assigns a
 number to each plot file.  Operation on plot files starts on file #1 and proceeds
 sequentially to file #10.  The open command must preceed the DATA command.  No
 actual plotting takes place until the PLOT command is issued at which time GRAPH
 calls PLOTIO.BAS to execute the commands for as many of the 10 plot files as are
 in use.
	EXAMPLE:	OPEN (1)
3	CLOSE
	CLOSE (n)
     After a command sequence on a plot file is over, the file must be
 closed.  Then and only then can a new file be opened and a command sequence
 to it be started.
	EXAMPLE:	CLOSE (n)
3	CHAIN "prog"
	From GRAPH one can chain to another BASIC program and return back
 into GRAPH provided the correct common blocks are observed.  Type HELP
 BASIC PLOT COMMON for more information.
3	DATA
	DATA filespecifier
     Before a file may be plotted, it firs must be defined.  The DATA 
 command assings the file name containing the data to be plotted.  Warning,
 if the name typed in does not exist a fatal error will occur and GRAPH will
 stop.  BASIC has almost no error recovery.
	EXAMPLE:	DATA DK!:TEST.DAT;1
3	PLOT
	After all commands for all data sets have been entered, the PLOT
 command will start GRAPH/PLOTIO to executing these commands sequentially.
 After the last command on the last file is done, GRAPH will return to input
 mode and accept more commands.
3	POINT
	POINT #N
     Each plot file has within it the type of symbol to plot it out with.
 If this command is never issued it is assumed that a line plot is desired
 (C(9)=0).  If it is issued, the type of symbol specified(0-3) stays with
 the plotfile thereafter.
3	LINE
	LINE #N
     Each plot file has within it the type of line to draw on the terminal.
 By default this value should be set=1(line plot).  Line plots may be disabled
 by setting LINE #0.  Type HELP BASIC PLOT LINE_TYPE for information on the
 values N may take for line plots.
	EXAMPLE:	LINE #1
3	WINDOW
	WINDOW(xmin,xmax,ymin,ymax)
     For defining the graphics terminal window(area of screen), all corrdinate
 values are taken to be in Screen Units(0 < x < 1023, 0 < y <780 ).  Data on a 
 plot file is never plotted outside of the window.
3	VIEWPORT
	VIEWPORT(Xmin,Xmax,Xint,Xtics,Ymin,Ymax,Yint,Ytics)
 
	Xmin,Ymin	minimum value on axix
	Xmax,Ymax	maximum value on axis
	Xint,Yint	axis value ot which the orthogonal axis intersect
	Xtics,Ytics	if > 0 # tics on axis and linear plot
			If < 0 # of cycles of log axis.
 
 Data outside the range of the viewport will not be plotted.  Data a
 factor of 30 outside the viewport will produce overflow errors.
	EXAMPLE:
		VIEWPORT(-5,10,0,3,1,1000,10,-3)
 Here the X-axis runs from -5 to 10 with three divisions.  The Y-axis
 instesects the X-axis at X=0.  Tye Y-Axis is logarythmic from 1-1000
 with three cycles.  The X-axis intersects the Y-axis at Y=10.
3	TITLE
     The TITLE command allows the user to specify an X-title and a Y-title
 for each axis of each graph.  The titles 'evaporate' if you ever exit GRAPH.
 After typing in "TITLE", the program responds with "X-TITLE and then prompts
 for input.  Then it prints Y-TITLE and promts for more input.
3	LIST
	LIST, LIST(N1,N2)
     To examine the plot file, the number of points, the viewport and the
 window, and the data itself is displayed by typing LIST.  This will list
 all data in array C(1019).  To get a list of just a section of the data from
 X-Y pairs N1 to N2, type LIST (N1,N2).
3	DELETE
	DELETE
     After a plot file is opened, the user may specify that after plotting,
 an unspecified # of points should be deleted.  After the plotting is done,
 (using a point plot helps), the graphic cross hair is displayed.  Center it
 over a pint and hit any key and the point is removed from the data set.
 (forever).  If the key "S" is hit, deleting points stops with the last
 point entered, otherwise deleting points continues unless the "RETURN"
 key is hit in which case no point is deleted.
	EXAMPLE:
		OPEN (1)			open data set 1
		DATA DK1:TEST.DAT		use this plot file
		POINT #1			do a point plot
		DELETE				set up for deleting after plot
		CLOSE (1)			close
		OPEN (2)			now use the same file over
		DATA DK1:TEST.DAT		and replot it
		PAGE				Erace screen
		PLOT				Display new plot
		
  **** warning this routine has a few bugs
3	ADD
	ADD
i
     The ADD command is the exact opposite in effect to the DELETE
 command.  With it points can be added to the data set.
 *********warning it does not always work well.
3	STOP
	STOP
     When this command is executed the program will stop execution
 and return to the BASIC monitor.
3	COPY
     When this special command is executed, a Hardcopy of the display
 (graph) will be made.
3	BYE
     BYE exits the user from GRAPH and BASIC.
3	HALT
	HALT is used in debugging PLOTIO.  PLOTIO stops after plotting the
 graph rather chaining bach to GRAPH.
