For OS it means that you should pick one abstraction for process state and one abstraction for IO and in fact you can have same abstraction for both. In this vi

For OS it means that you should pick one abstraction for process state and one abstraction for IO and in fact you can have same abstraction for both. In this view Plan 9 makes sense while modern Unix with files, sockets, AIO, signals, various pthread and IPC primitives and so on does not (not to mention the fact that on every practical POSIX implementation various such mechanisms are emulated in terms of other synchronisation mechanisms)