Graphically Speaking
There is now a variety of plotting packages on Bama, and there are several others that can be added in the future. These range from interactive, command driven programs to callable subroutines. Some are "native" to the Sun operating system and we have added to the list from outside sources. Before going into the information on the graphing packages a word or two about output is in order.
The graphics packages are there to provide you with more sophisticated output than can be produced on a simple terminal. There was a time when terminals were for words and graphics terminals were for graphs. Out of that came a movement to get graphics into text terminals. And now, of course, we don't use real terminals, we use telnet programs or X-windows that simulate terminals, to connect to Bama. The terminology of graphics output is a legacy of this history. Of course, you must also bring into the picture the whole variety of printers that produce hardcopy (i.e. paper).
When you run a graphics package you will need to make a choice about how you are going to view your graph. We'll simplify here by assuming you are working through a telnet session. The most common option now for plotting is to open a "Tektronix" window. Why? Because a very popular line of graphics terminals was produced by Tektronix, Inc. They set up a standard for graphics commands that has been adopted quite widely. In order to view your graph on your PC, then, you will have to have a Telnet program that supports "Tektronix" capability. The generic telnet program that comes with Windows 95/98 does not have any graphics support, so you will need to get a more fully featured telnet program. The computer center has been distributing TeraTerm as a better alternative. On TeraTerm, under the "control" menu (across the top of the window) there is an "Open TEK" option. This will open another window that will be your graphing window. Some graphing software will be smart enough to switch over to this wind
In the graphics package you are using you would want to look for references to creating output for "tek" or "401x" where x is some number, or some other variation on this. There were other graphics options that were added into graphics terminals, such a "Retrographics" or "Regis", and you will see those referred to, but they are not common anymore. When you have these two pieces set correctly, the telnet program and the graphics software, you will see the graph produced correctly on your "terminal."
Producing a hardcopy plot depends on the type of printer available to you. The program will produce a file with the printing commands that you would then send to the printer with the usual Unix printing command (lp). Most printers speak their own language but there have been attempts to standardize. Many now can use the Postscript language (introduced by Adobe). You will see this as an output option on many graphics packages. The printer call "afccu2" on Bama is a postscript printer. Printers from Hewlett Packard, while they might understand Postscript, will use their own printing and plotting languages, PCL and HPGL, respectively. Successful printing of your graphics requires that you match the output device in the software to the capabilities of your printer.
Graphics Software
The Sun system has some simple graphics packages. Two which you might of use are "plot" and "graph". They are pretty basic. There are man pages available for both of these.
In addition we have added gnuplot. This is interactive software that lets you read in data, format the graph and print it out to a variety of printers or to your terminal. It can also graph mathematical functions. There is a man page available for this and it has help information built into. Start the program by typing
gnuplot
then type help to find out more about what to do next. You might also look at the man page for "lasergnu" for another way to print gnuplot graphs.
For users who are working with their own programs we have added a library package called "pgplot". It is an excellent technical package and it can do a wide variety of quite sophisticated graphs, including 3-D graphs, contour plots, and grayscale representations. It can also do color graphics on output devices that support full color. This package can be used with both Fortran and C. Help is available on the Web starting at
Just follow the link to software. There are demonstration graphs illustrating what the program can do, as well as sample programs showing how it is used.
In addition, pgplot has subroutines that let you write your own interactive plotting software. For instance, you can interact with the cursor, taking input from its position.
On the high-end of graphics software is OpenGL graphics library. This is an image-rendering package that has now becoming a standard. Vendors are still personalizing it, however, so that OpenGL software that runs on one type of machine may not work on another. For instance, SGI software written for OpenGL will not work on the Sun version. SGI has customized some of the routines. We can install the run-time libraries for this so that if you have received software from some place that called the subroutines, they could be made to work. Installing the full working environment so that you can develop your own programs requires that we buy additional software, but this can be done if the need arises. Realizing the full potential of this software requires specialized graphics hardware, but it will still work with generic X-windows terminals.
For more information and updates on graphics software, please go to the software web page. You'll find a link to it from http://bama.ua.edu/~unixinfo
© 1999, The University of Alabama. The information included here is for the University of Alabama central computing facility as it was configured on the document date. It may or may not apply to other Unix systems.