PAUSE
BOX
ILLUSTRATION
GO
We already know that a file is a
collection of data stored on a storage
device such as disk or magnetic tape.
A collection of files on the storage device
can be referred to as a file system.
Assume that a lesson in this tutorial is composed of three integral parts:
presentations,
Lesson
--------------------------------------------
| presentations |
| ------------ |
| | tpc1 | |
| | tpc2 | |
| | tpc3 | |
| | : | |
| | tpcn | |
| ~~~~~~~~~~~~ |
|___________________________________________|
presentations, illustrations
Lesson
-------------------------------------------
| presentations illustrations |
| ------------ ------------ |
| | tpc1 | | fig1 | |
| | tpc2 | | fig2 | |
| | tpc3 | | fig3 | |
| | : | | | |
| | tpcn | | | |
| ~~~~~~~~~~~~ ~~~~~~~~~~~~ |
|___________________________________________|
presentations, illustrations and reviews.
Lesson
--------------------------------------------
| presentations illustrations reviews |
| ------------ ------------ ---------- |
| | tpc1 | | fig1 | | rev1 | |
| | tpc2 | | fig2 | | rev2 | |
| | tpc3 | | fig3 | | | |
| | : | | | | | |
| | tpcn | | | | | |
| ~~~~~~~~~~~~ ~~~~~~~~~~~~ ~~~~~~~~~~ |
|___________________________________________|
The above organization shows a 3 level hierarchy.
On Level 1 are tpc1-tpcn, fig1-fig3, rev1 and rev2.
On the Level 2 are presentations, illustrations and reviews!
And at the top of the hierarchy is the principal entity, the Lesson!
This representation may be easier to conceptualize if we use
the inverted tree approach.
Let us begin at the bottom level by considering
topics, figures and reviews as ordinary files.
| | | | | | | |
tpc1 tpc2 tpcn fig1 fig2 fig3 rev1 rev2
From there we can build the 2nd level by considering presentations,
illustrations and reviews as directory files.
| | |
presentation illustration reviews
| | |
| | |
~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~ ~~~~~~~~~~~
| | | | | | | |
| | | | | | | |
tpc1 tpc2 tpcn fig1 fig2 fig3 rev1 rev2
Then finally we can build the top level where
Lesson is another directory file.
Lesson
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | |
presentation illustration reviews
| | |
| | |
~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~ ~~~~~~~~~~~
| | | | | | | |
| | | | | | | |
tpc1 tpc2 tpcn fig1 fig2 fig3 rev1 rev2
The above representation is called a hierarchical file system.
From this simplified illustration you can see the UNIX
directory structure and also note the fact that directory
files may hold both directories and ordinary files!
In other words, the directory Lesson holds three directory
files: presentations, illustrations, and reviews.
The directories presentations, illustrations, and reviews, hold
ordinary data files as shown in the figure!