I'm not quite sure, but I think I remember reading that CoW (Copy on Write) was not there in the earliest Unixes. Might have been implemented at Berkeley some t

I'm not quite sure, but I think I remember reading that CoW (Copy on Write) was not there in the earliest Unixes. Might have been implemented at Berkeley some time later. Seem to remember reading this some years ago when reading about fork, because without CoW, fork's copying was expensive, particularly if you were going to exec another program in the child just after forking.