Most people seem happy to start with the GDL Cookbook 3 by David Nicholson-Cole.
https://www.nottingham.ac.uk/~lazwww/cookbook/CB_download/cookbook3download.html
It is a bit old now but still relevant.
There is also “Introduction to Object Making with ArchiCAD: GDL for Beginners” by the same author (again a little old but still good).
https://support.graphisoftus.com/files/GSNA/Books/Object_Making.pdf
Both of these are free resources.
There is also a GDL Handbook from CADimage by Andrew Watson if that is still available – but that will cost you if it is.
https://www.cadimage.com/Other-Products/gdl-handbook
There is of course also the GDL Centre where you are now for this forum – follow the links at the top of this page.
Barry.
Versions 6.5 to 22
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