The plot as well as the axes are active areas which allow zooming, panning, scaling, and paging. To read and write binary files you need this patch . It does not need the patch mentioned above, because 2.4i can read binary data. However, this version cannot handle ascii data any more. But there is an rpm available.
Older versions are also available.
No compilation is necessary. Nep is pure Tcl, given that you have installed the BLT-extension.