@ezio There are three different Sun Unix operating systems. The first (very early on) was a straight port of V7 Unix by Unisoft (just like a lot of other vendors), then Sun hired a bunch of the early BSD developers from CSRG and made a BSD derivative called SunOS. This continued until AT&T invested in Sun buying out something like 15-20% of their common stock. A condition of the investment was that they had to kill off the BSD-based SunOS and base the next major version (SunOS 5) on SysVR4 and that operating system (SunOS 5.x) was branded Solaris in marketing copy to differentiate it from the BSD-based SunOS that came before.