1), No, msvc does not have gnu plot
gnu plot is completly seperate, you can use GNU plot to draw graphs, but you'll have to download it and setup the project to work with the settnigs to make it work, (that makes very little sense I know)...
2) you can find out about GNU plot here.
Documentation on the project can be found here (http://gnuplot.sourceforge.net/docs_4.1/)
but as far as integratnig it into VC++ I've not tried so I can't realy help, in fact this is really the first time I've even thought of using GNU plot, as in past projects I've used GD objects to draw graphs and saved then as Jpgs. -though give me a few months and I might have decided that GNU plot is the next best thing snice sliced bread,
3), I really couldn't tell you, but I miagine that you'll out the equations in the program, the program will figure out the points to plot, pas that on to GNU plot, and the plotting will take place in a seperate window, (that's how it'd usually be done) (I think)
(does anyone know if it can plot interactive refreshing graphs in realtmie?).
For different working enviornments, I don't think so, (though I may not have grasped the question.)
if you write ANSI C it will compile on any C compiler, any machine, the bianry can then be run on any simillar machine,
so simple hello worlds compiled on windows can run on any wnidows machine, cmopiled on mac can run on any mac etc.
the problem is that yuo'll e introducnig outside binary files and pre-compiled libraries to your project for the GNUplot part, so you'l need the GNUplot libraries that you use on all the machines you intend to run on.