The interfaces Wr and Rd provide object-oriented output
and input streams, called writers and readers. These were
invented by Stoy and Strachey in 1972 [OS6part2] . The versions
presented here are slight modifications of the versions in the first
Modula-3 book [SPwM3] . We also present related interfaces for
obtaining writers and readers connected to texts or files (
TextWr, TextRd, FileWr, and FileRd), for accessing
standard streams (Stdio), and for performing I/O in simple
programs (IO). The interfaces FileWr and FileRd
supersede the interface FileStream in [SPwM3] .