Common Lisp the Language
2nd Edition
A stream is a source or sink of data typically characters or bytes. Nearly all functions that perform I/O do so with respect to a specified stream. The function open takes a pathname and returns a stream connected to the file specified by the pathname. There are a number of standard streams that are used by default for various purposes. See chapter 21.
X3J13 voted in January 1989
(STREAM-ACCESS)
to introduce subtypes of type stream:
broadcast-stream
concatenated-stream
echo-stream
synonym-stream
string-stream
file-stream
and two-way-stream are disjoint subtypes of stream.
Note particularly that a synonym stream is always and only of type
synonym-stream
regardless of the type of the stream for which it is a synonym.
