ArchiCAD offers an integrated development environment (IDE) for easy access to the object's source code. Each part of an object  - such as the different scripts, binary stuff and pictures are concentrated in one editor panel. You edit via the file menu item "Open Object".

But these built-in editing functions have a number of shortcomings and you need to be running a full license version of  ArchiCAD.

There were two main external "full featured" editors developed out there (Black Turtle and 3nF Scripter), but both have stopped development and neither will recognize GDL syntax for versions more recent than about ArchiCAD 7. They are no longer recommended.

 There is a not fully external editor, but an project development structure to use at least an external script editor. See here: GDL Nuke - Object Fission&Fusion.

You can find links to further GDL development tools on this page: www.gotogdl.net

You can edit script text in a simple text editor too, but you have to copy and paste all text from the IDE to the editor and back. This only makes  sense if you are editing large projects or want to anaylse exisiting scripts with the extended text editing features of the external software.

Windows

I recommend Proton (download) for which I offer an extension for syntax highlighting. This has to be copied into the syntax scheme folder of the proton program folder. It  automatically highlights commands, variables, Text, comments and global and optional parameters in different colours and/or styles.  Extension download see below.

MacOs

Owen Sharp has done the same for the (commercial) TextMate editor. See the discussion in ArchiCAD-Talk. He kindly permits to offer it here for download. There are quite a few quirks with the implementation, but worth to try. Improvements please return to us or the author.

The zip to download contains two files, a bundle and a theme file, which live in the following folfers:

~/Library/Application Support/TextMate/Bundles
~/Library/Application Support/TextMate/Themes

Platform Independent

A top recommendation is Sublime Text. It is a commercial very powerful source code editor with a lot of available plugins. The GDL package can be installed by a package control plugin, directly imported from github or the download link below. See discussion and links in the German ArchiCAD forum.

And there is still VIM outside. The powerful editor out of the linux world. We are in contact with someone, who wants to teach vim the GDL syntax. If he has finished, he wants to share the config files. We will inform you here.