Abstract: headers are there, not much else. I moved the IDO 5.3 IRIX4 files over to my P.I. and started playing around with them, and there is mixed news. Bits of IDO4.1 (the recommended IDO for IRIX 4) are there, including headers and cc, but other bits are missing (make, gendist, and other stuff that make life easier.) So news is mixed: it looks like you could concievably use the IRIX4 files on the freely-distributable IDO 5.3 to get a lot closer to having a development environment on IRIX 4.0.x, but you'll still need to supplement (big time) with GNU tools. I have the tarfile of the IRIX4 subrelease here if anyone wants it, but I don't think I'll put too much more work into making it nice. I use 3.3.2 more often on that machine, anyway. I believe there is also a way to cross-build on an IRIX 5 host.