Files
and drives: definition, naming, extensions
Files
- All information on your
computer (except that in ROM) is stored in a file.
- There are two parts
to a file– the name and an extension. For example, 'test.txt' might be
a file named 'test' - the extension is 'txt'.
- The name should be descriptive
of the contents of the file - this makes your life simpler. You then don't
have to open the file to see what's in it. WARNING - older computer systems
have limitations on filenames - 8 characters, no special characters (!@#$%^&*())
or spaces. The same is true of subdirectories. Remember this - even newer
software has legacy (old) code which will crash. WARNING AGAIN:
GIS software has tons of legacy code scattered here and there. Remember these
limitations and apply them to ALL your GIS work. It may well save your buns
at some point.
- The extension tells
the computer what sort of file it is.
- For example –
Word files (.doc), executables (.exe), batch files (.bat) etc…
- Limited to 8 characters
+ three for the extension in DOS. This is the old stuff. Use it!
- Windows 95 and newer
allows long filenames (and the Mac OS). However, remember, the fact that
the OS allows it doesn't mean the application will.
Drives:
- A computer typically has a number of different mass storage locations -
think of these as your 'drives'. Some may not even be on the computer at which
you sit - they are what we call 'network drives'. They are harddrives which
sit on another computer, but which you can access. As an example, let's go
over what's available in our lab:
- A:\ drive. This is your 3.5" floppy drive.
- C:\ drive. This is where the OS and application software resides. Harddrive
- D:\ drive. Another harddrive. Well, not really - it looks like one,
but it is really half of the one physical harddrive in these computers.
What happened is that the harddrive was 'partitioned' into the C:\ and
D:\ drives. The D:\ drive is public - EVERYONE sitting at that computer
has both read and write access to everything on that drive.
- E:\ drive. CD/DVD drive.
- F:\ drive. Zip drive.
- G:\ drive. If you plug something in (ie, usb flash drive), it will be
mapped to this letter.
- J:\ drive. A network drive. You have only READ access - meaning you
cannot change any of the files on this drive. This is where we keep data
for the class. To use it, first copy it to your personal drive (zip, usb,
etc).
- K:\ drive. Another network drive. We call this the transfer drive -
everyone has full READ/WRITE access. In other words, it's public. Never
work from this drive, as someone will delete your work. It's purpose is
to put info there for someone else to grab. For example, if you have a
question, drop your file onto the K:\ drive and wander into my office.
I can access it and, hopefully, answer your question.
Directories
- how files are organised
on your computer. A 'Path' is the address to a particular subdirectory.
A good analogy is the filing cabinet. Each filing cabinet is a different drive.
Each drawer is a first level subdirectory, then you enter folders within the
drawer, finally reaching the file itself.
- An example of a 'path' would be C:\bobstuff\photos\bob.jpg Thus,
the file 'bob.jpg' is located on the C:\ drive in the 'bobstuff\photos\ subdirectory.
- To manipulate files, use 'Windows Explorer' - accessed by right-clicking
on the start icon (bottom left of your screen) then 'explore'. MAKE
SURE you know how to use windows explorer to access different drives/subdirectories/files.
This is absolutely fundamental to everything you do on a computer. Let me
repeat. DO NOT USE "my computer" or some other such
garbage. DO USE Windows Explorer. It will make your life much
easier when working in a multiple drive environment (basically, the GIS world).
Basic Explorer tutorials at: