[dhs12345]

You might find the below link interesting. Zoom in.

Also, I am not able download it reliably. Probably due to my version of Acrobat.

https://www.levenez.com/unix/unix.pdf

[Swordmaker]

You might find the below link interesting. Zoom in.

Thanks, dhs12345, it is quite interesting. As I said, Mac OS X, soon to be called AppleOS, is one of the few UNIX™ that is fully POSIX® certified UNIXes left.

i had no problem zooming in or downloading. The Macs use display PDF so it makes things much easier to handle PDFs. Again, thanks for that quite interesting overview of the UNIX development and family tree.