     A directory is a catalog of "segments." It serves like a file drawer,
with segments being the file folders in that drawer.  There are many
directories on Multics, some of them indigenous to Multics and others created
by users.  Each contains its own segments.  No two segments in a directory can
have the same name, but like-named segments can be kept in separate
directories.

     Directories also catalog other directories, thereby creating hierarchies
of directories.  For example, a directory named Smith could have three or
four directories under it, and those directories in turn could have
directories under them.  The hierarchy of a particular set of directories is
indicated by the greater-than character (>).  For example, the order of two
directories under Smith is:

Smith>directory_1>directory_a

This indicates that directory_1 is a directory under, or contained by, the
directory Smith and that directory_a is a directory under directory_1.
A segment contained in a directory would be in the last place in the line of
directories.  For example:

Smith>directory_1>directory_a>my_segment

If you wanted to indicate that the segment is in directory_1, you would
represent the hierarchy as follows:

Smith>directory_1>my_segment

A directory name cannot follow a segment name because directories are not
contained in segments.

     Directories are created with the create_dir "command." Names on
directories follow the same conventions as those on segments: they cannot
contain blank spaces and uppercase letters are distinguished from lowercase
letters.
