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] .