PRO xy

X = FltArr(40)
Y = FltArr(40)
names = StrArr(2)
symbols = FltArr(2,12)
array = FltArr(2,40)

The names will be read in from the data file, however, they were preformatted for use with disspla.  I re-interpreted them here in the program which produces the graph.
namex = '!7D!6!Dr!NS!9%!6/ (J K!E-1!N mol!E-1!N)'
namey = '!7D!6!Dr!NH!9%!6/ (J K!E-1!N mol!E-1!N)'
The errors associated with the data had the high and low values generated already.  Here I manually calculated what the +/- values were for each data point.
errX = [2, 3, 1.4, 1.4]
errY = [0.6, 0.7, 0.4, 0.4]

The data file is opened here.
OpenR, lun, 'example', /Get_Lun
Point_Lun, lun, 0
The data file is read here.  The entire file is read and the values placed into the variables listed after "lun."
ReadF, lun, nsets, names, nscl, symbols, array
The FltArr named "array" contains all of the two columns of data.  X is being set to the first column of data, whereas Y contains the second column of data.
X = array(0,*)
Y = array(1,*)
Free_Lun, lun

Arrays X & Y are reformed so they are changed from column vectors into row vectors.
X = Reform(X)
Y = Reform(Y)

The two columns of data that were read into "array" then transfered into 2 one-dimensional arrays, X and Y, contain various different types of data.  It turns out that only the first 4 numbers are points that will be plotted with circles.  Then, "-1"s were used to separate the data into sets.  Those -1s are skipped and not read.  The 4 points, subscripted from 5 to 8 are plotted by plusses and are read into their own array.  Finally, two lines are drawn with the final set of data.  Note the really convenient syntax where you can read portions of an existing array without using a loop!
CircX = X(0:3)
CircY = Y(0:3)
PlusX = X(5:8)
PlusY = Y(5:8)
LineX1 = X(34:35)
LineY1 = Y(34:35)
LineX2 = X(37:38)
LineY2 = Y(37:38)

I modified the existing code to do something a little bit different.  This shows you the opening to a myriad of minor variations.
Print, '1 = Tektronix 4014'
Print, '2 = Printer'
Print, '3 = Postscript file and potential printing'
Print, 'Which device do you want?'

CASE whichdevice OF        There are 3 choices, so I'm using a "CASE" statement
'1': Begin
Set_Plot, 'TEK'
DEVICE, /TEK4014
End
'2': Begin
Set_Plot, 'printer' ;Use the DIALOG_PRINTERSETUP function to define parameters
End
'3': Begin
Set_Plot, 'PS'
DEVICE, FILENAME = 'ertest.ps'
DEVICE, /INCHES, XSIZE = 7.5, YSIZE = 8, \$
XOffset = 0, YOffset = 0
For the postscript file I am changing the axis titles to use postscript fonts
!p.font=0
namex = '!9D!18!Dr!NS!Eo!N!18/ (J K!E-1!N mol!E-1!N!18)'
namey = '!9D!18!Dr!NH!Eo!N!18/ (J K!E-1!N mol!E-1!N!18)'
End
Else: Print, 'Not a device'
EndCase

If (whichdevice EQ 1) Then Begin
Set_Plot, 'TEK'
DEVICE, /TEK4014
EndIf Else Begin
Set_Plot, 'PS'         Output goes to a postscript file
DEVICE, FILENAME = 'xy.ps'         Name the postscript file ending with .ps
DEVICE, /INCHES, XSIZE = 7.5, YSIZE = 8, \$
XOffset = 0.002, YOffset = 0.05
EndElse

!p.charsize=2                     Make text twice the default size
A = FIndGen(16) * (!PI*2/10.)     Generate the symbol for a circle
UserSym, cos(A), sin(A)

Plot, CircX, CircY, XTITLE = namex, YTITLE = namey, \$
XStyle = 1, XRange=[-40,10], \$
YStyle = 1, YRange=[-20,-8], Max_Value=-8, \$
SymSize=1.5, PSym = 8
OPlot, PlusX, PlusY, PSym = 1,
OPlot, LineX1, LineY1, PSym = 0,
OPlot, LineX2, LineY2, PSym = 0, LineStyle=1  Here the linestyle is changed to dotted.
xyoerr, X, errX, Y, errY        Call the special function written to plot both x and y error bars
If you put a comma after errY, you can add a number for the LineStyle and the Thickness of the line, but these are optional.  (e.g., xyoerr, X, errX, Y, errY, 2, 4). The defaults for not describing them are a solid line of normal thickness.

If (whichdevice EQ 2) Then Begin     You need to close the document for the graph to actually go to the printer
DEVICE, /Close_Document
EndIf

Now that the PostScript file has been opened, you need to close the file.  Then you are prompted as to whether or not you want to print.  Any other key pressed besides y will not result in printing. (eg. "n" or "1" will both not print).
If (whichdevice EQ 3) Then Begin
DEVICE, /Close_File
toprint = ''
Print, 'Y or N'
Print, 'Do you want to print?'