The interpreter is the "engine" that executes scripts.
Download the latest version (4.66) from this site.
EDIT (MS-DOS), Notepad (Windows), E (OS/2), or any other ASCII editor will do.
Basically, a KiXtart script is just an ASCII text file with a ".kix" extension, containing the KiXtart code.
More "advanced" editorsdo help make scripting a lot easier.