With the exception of the original "library" file system, most of the file systems in the IFS store their objects in the "loosely-defined" file structure that's common in Windows and UNIX environments. This type of object is known as a "stream file" because the data in it is thought of as "one continuous stream of bytes." In other words, there's a start of the file, and an end to the file, but nothing else is defined. A program can use this big, long string of bytes for any purpose that it likes.