# I/O Streams

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] .

- The IO interface
- The Wr interface
- The Rd interface
- The TextWr interface
- The TextRd interface
- The Stdio interface
- The FileWr interface
- The FileRd interface