Rexx Programming/How to Rexx/io

In rexx, input and output is treated as character streams. Characters within a stream appear in the order in which they were provided.

Transient streams
Characters from transient streams can only be read once. The terminal keyboard is an example of an input source that produces a transient stream. Once the characters have been read from a transient stream, they disappear from the input source.

Persistent streams
Characters from persistent streams can be read multiple times. Files are considered to be an input source for persistent streams. It is possible for files to be read multiple times. The input characters from the file will be obtainable throughout the lifetime of the file.

Input streams
Characters within a stream appear in the order in which they were provided.