I presume you're working in a Windows enviroment, you could use GDI/GDI+ from the Windows API, GDI/GDI+ can be called from C/C++. Here's an example of a plotter on screen using C# (this can be translated to either C or C++).
**broken link removed**
The graph could then be saved to a BMP or a WMF, you'd have to look up how to do that with the Windows API.
Also have a look at this:
**broken link removed**
Or if you're only interested in output of a graph
What you could do is bundle GNUPlot with your program and make it silently invoke GNUPlot to create your desired output. To download GNUPlot go to
http://www.gnuplot.info.
Have a look here on some discussion on how to do it from C++:
**broken link removed**
You can make GNUPlot output a graph to a bitmap like a PNG, BMP or even Postscript.
- Jayson