If you want the "official" editor, you can use Ti Graph Link (it must be somewhere on http://www.ti.com/calc, it works with all windows version I know), but this one seems better : http://www.tiedit.tk/.
To send your programs to the calculator (you don't need to do this while programing, have a look at Virtual Ti : http://www.ticalc.org/archives/files/fileinfo/84/8442.html), you'll need Ti-Connect (or any other ti<->pc link software).
