The PDP-11 backend for GCC is a decade out-of-date with the rest of the changes in the compiler. Updating it ought to be straightforward, but nobody's stepped up to do it. Alternatively, you can use the PDP-11 backend with the matching version of the GCC front end, but I don't see any decade-old versions of the front end at the traditional GNU distribution sites. You also have to keep in mind that GCC doesn't come with a PDP-11 C run-time library. Not a problem if you're writing an OS from scratch and will be writing all the libraries too. Too bad you're giving up on RT-11 so quickly - there's several hundred megabytes of freely-distributable code available for it in the DECUS collections. I don't see why not - especially if you're using (for example) the free PDP-11 DECUS C compiler - as long as you anything you use the code for would come under "hobbyist". The DECUS C compiler is quite capable, and many major packages have been written in it. -- Tim Shoppa Email: shoppa(a)trailing-edge.com Trailing Edge Technology WWW: http://www.trailing-edge.com/ 7328 Bradley Blvd Voice: 301-767-5917 Bethesda, MD, USA 20817 Fax: 301-767-5927