It is these exceptions that give RE's such power and flexibility. It is outside the scope of this paper to document all of them. The more common ones are explained. Mostly just learn one way of doing an RE and do not try any others and you will hardly ever need to worry about exceptions. A process can be the command line, a program, a file, or a monitor screen, to mention a few.
Processes can also exist within another process.
For example, in a high level language, an assignment statement within an if statement where the value of the assignment is passed to the if statement for testing. Also good to understand is that streams can be contained inside streams. In fact, that understanding is crucial for the rest of the paper. A stream has two types, data and control commands. Data and control commands can range from binary bits to paragraphs.