And all the other mainframe operating systems ... Most of the other big mainframe companies tried to emulate IBMs walled garden each had their own OS, their own

And all the other mainframe operating systems ... Most of the other big mainframe companies tried to emulate IBMs walled garden each had their own OS, their own (incompatible) networking system, their own compilers etc Unix was great mostly because it was simple and you could port it to new hardware ... Prior to that it was in no hardware manufacturer's interest to release their OS into the wild, that didn't sell mainframes. Unix also released a generation of frustrated systems people who were not allowed to write kernel code unless they worked for a mainframe company