Euphoria program files are simple text files. You can create these text files using any text editor you desire. For starting out, I recommend using RDS' own "ed" editor. If you have installed Euphoria properly, you can simply type ed <filename> to create/open a text file. You can use ed from Windows, DOS, or Linux/FreeBSD. What's cool is that ed is completely written in Euphoria.

For a Windows-only editor, written completely in Euphoria, try Edita by Pete Lomax.

You can search the Euphoria programs archive for more editors written in Euphoria, or check out Euforum, where programmers editors have been discussed before.