I used to work for a firm creating software for handling patient's data in hospitals. Mainly using Xenix, all software source was controlled via the Revision Co

I used to work for a firm creating software for handling patient's data in hospitals. Mainly using Xenix, all software source was controlled via the Revision Control System, part of the OS. R.C.S allowed earlier versions of source to be generated easily, when required. All devs using R.C.S accepted it and used it easily, many times each day.