Gnuplot  

Gnuplot is a command-line driven interactive function plotting utility for UNIX, MSDOS, and VMS platforms. The software is copyrighted but freely distributed (i.e., you don't have to pay for it). It was originally intended as graphical program which would allow scientists and students to visualize mathematical functions and data. 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. The interface includes command-line editing and history on most platforms.

For more detail, please visit the offical site of Gnuplot.