Why does the Apple MacIntosh have two operating systems? I'm planning to switch to a Mac whenever Apple gets its act together about the new processors, but I'm concerned about the apparent need to have two operating systems--Unix and OS-X. So the following dumb questions: Isn't this inefficient? Wouldn't it be better if Mac software ran directly from Unix? The desktop interface could also be a program running from Unix, like X-Windows. Any Mac software could be run from the Unix shell (shades of DOS). The result of having to use two operating systems is a huge memory requirement and a system slowdown, no?