When writing a network application you can use non-blocking mode or blocking mode. Non blocking mode is more flexible and required when the application has to do multiple things, like servicing multiple sockets.
For over 25 years, the name VOS has referred to an operating system that is reliable, continuously available, and easy to use. We did not take the decision to rename VOS lightly. The new name acknowledges another important trend has taken place over the last 10 years.