What does stream mean? What are its characteristics?

c# c++ class stream terminology
Kashif picture Kashif · Feb 28, 2011 · Viewed 18.8k times · Source

C++ and C# both use the word stream to name many classes.

  • C++: iostream, istream, ostream, stringstream, ostream_iterator, istream_iterator...
  • C#: Stream, FileStream,MemoryStream, BufferedStream...

So it made me curious to know, what does stream mean? What are the characteristics of a stream? When can I use this term to name my classes? Is this limited to file I/O classes only?

Interestingly, C doesn’t use this word anywhere, as far as I know.

Answer

Marc Gravell picture Marc Gravell · Feb 28, 2011

Many data-structures (lists, collections, etc) act as containers - they hold a set of objects. But not a stream; if a list is a bucket, then a stream is a hose. You can pull data from a stream, or push data into a stream - but normally only once and only in one direction (there are exceptions of course). For example, TCP data over a network is a stream; you can send (or receive) chunks of data, but only in connection with the other computer, and usually only once - you can't rewind the Internet.

Streams can also manipulate data passing through them; compression streams, encryption streams, etc. But again - the underlying metaphor here is a hose of data. A file is also generally accessed (at some level) as a stream; you can access blocks of sequential data. Of course, most file systems also provide random access, so streams do offer things like Seek, Position, Length etc - but not all implementations support such. It has no meaning to seek some streams, or get the length of an open socket.

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