gnuplot can be used interactively, or it can be run with a command file, either hand constructed or saved from an interactive session. [The GNU in gnuplot is NOT related to the Free Software Foundation, the naming is just a coincidence (and a long story). Thus gnuplot is not covered by the Gnu copyleft, but rather by its own copyright statement, included in all source code files.]
Gnuplot handles both curves (2 dimensions) and surfaces (3 dimensions). Surfaces can be plotted as a mesh fitting the specified function, floating in the 3-d coordinate space, or as a contour plot on the x-y plane. For 2-d plots, there are also many plot styles, including lines, points, lines with points, error bars, and impulses (crude bar graphs). Graphs may be labeled with arbitrary labels and arrows, axes labels, a title, date and time, and a key. Plots may be saved in several formats, including postscript.
Gnuplot has a built-in help system (type help at the gnuplot> prompt).
See Also: