Re: DOS era?
> In the physical world a directory would be represented by a
Directory.
Like, you know, a University directory, a book with a chapter full of the names of staff, directing you to the department they belong to. And a chapter with a list of all departments, directing you to a page which describes the department, including the building(s) they are housed in. And a chapter with a list of all the buildings, directing you to the square on the map where you find the building represented.
Or a company directory, with a chapter listing all the members of staff, directing you to which desk they sit at.
You get the idea? A "directory" is something that directs you to where (or how) to find something (or someone) if you know what the name is.
Or, and bear with me on this, you may find this a bit complicated, a telephone directory, aka the Phone Book: a big fat book full of the names of people in a city/region, in alphabetical order, with their phone numbers. Or the Yellow Pages directory: a big fat book full of the names of companies in a city/region, in alphabetical order, with their phone numbers. Or the towns and villages directory: a big (but not very fat) book of the names of all the (small) towns and villages in alphabetical order, with the name of the city or region whose phone book/Yellow Pages included that town or village.
Gosh, you could almost say that those directories are "nested" or perhaps "multi-level".
Let's go back to the University directory: the page for a department also lists the number for the departmental secretary's phone. If you can remember the secretary's name, you can look them up in the Phone Book for the town/city the University is in OR if you only remember they are the Maths Dept. secretary you can look them up in the University directory, following the path described above.
Tada! You have two distinct and separate sets of directories, maintained by two completely different groups (the GPO for all the national Phone Books, the University for their directory) AND THEY BOTH LEAD YOU TO THE SAME THING, they both end with a pointer/address/unique identifier/phone number which, if you invoke/dereference/dial will get to access to all the data contained within (via a nice conversation with the secretary, maybe over a cup of coffee after a nice dinner out, followed by a show and a moonlit walk along the river).
You might be winding yourself up to say that, in the digital world, you would do all that using a database, not directories. Tell you what, you go off and read up on how file systems work, the big complicated ones we use on terabyte drives, the sorts of data structures they use to store the directories. Then try looking up those same data structures, but this time in the Boys Big Book Of Databases. Guess what you'll discover!
> There is evidence that before the existence of a directory|folder|thing-to-put-things-in that only the word "directory" existed for analog storage.
Yer wot?
Maybe you'd better *stop* taking the dried-frog pills; I don't think you are really Bursar-level material.