"IO Streams: Abstract Types, Real Programs."
    Mark R. Brown and Greg Nelson.
    November 15, 1989.  46 pages.

Authors' Abstract

    The paper proposes standard Modula-3 interfaces for text input and
    output.  It also describes an implementation of the interfaces,
    focusing on two novel features of Modula-3: the partially opaque
    type and the explicit isolation of unsafe code.