A bit of proofreading caught some small errors which were not in the original:

    - "This this invokes" -> "Thus this invokes"
    - "the standard output had occurred" -> "the standard output that has occurred"
    - "without typing up a console" -> "without tying up a console"
    - "The Shell, as command" -> "The Shell, as a command"
    - "late a night" -> "late at night"
    - "source programs has something" -> "source program has something"
    - "which states its contents" -> "which states it contents" [sic]
    - "In sincerely" -> "I sincerely"