Effect

I use the word "effect" to refer to communication between a Process and the rest of the world. Many other people use the term "side effect" for this. EricNormand uses the term "action".

Effects can be the process acting on the outside world (sending an email, writing to a file), or the outside world acting on the process (telling it the current time, feeding it user input events). Often the communication is conversational: the process will ask for some information, and the OS or other RuntimeEnvironment will suspend the process, go get the information, and resume the process with the information supplied.