Hardware Reference
In-Depth Information
no matter what else is trying to run. Some flight-control systems still use a CMT-based operating environment.
Another defining characteristic of RISC OS is that it relies heavily on the WIMP concept; if you have spent any time
on Apple's OSX you're not going to feel too far from home on RISC OS. WIMP is short for windows, icons, menu,
and pointer, which is a graphical user interface design that relies heavily on the use of a mouse and the drag-and-
drop principle. The WIMP style of interaction was first developed at Xerox in 1973, although the operating system
that popularized this style was of course Apple's Mac OS. Designers of WIMP interfaces pride themselves on the
interfaces' abstraction and ease of use. For example, to install new applications you simply drag the binary file into
the filesystem. To run the exact same application you just launch it from the filesystem where you copied it.
On the topic of filesystems, RISC OS uses a filesystem called Advance Disk Filing System, or ADFS for short. ADFS is
by far the most limited filesystem in this chapter. For example, you won't be able to put a few hundred files into a directory
or make use of that new 1-TB hard disk you have, nor will you be able to rip a DVD to the filesystem in one single file. These
points aside, there are a few small things you need to know about ADFS in order for you to be able to use it efficiently. The
first and most confusing part of ADFS is how a filesystem path first looks. Take, for example, this path:
ADFS::HardDisk4.$.Mystuff.Pi
This looks a little confusing at first so Table
11-1
breaks down the layout for you.
Table 11-1.
An example of a filesystem path broken down
Path Element
Definition
Filesystem Delimiter
ADFS
::
Filesystem type
HardDisk4
.
Device name and number
$
Root of the
HardDisk4
device
.
Mystuff
.
A directory under the top level of the filesystem
Pi
A file
None
The first thing you may have noticed is that parts of the path use different delimiters, unlike in Unix or Linux
where all paths are delimited by a forward slash
/
. The filesystem type and the physical device are delimited by
::
.
Thankfully you won't need to worry too much about this delimiter unless you are changing between physical devices
or network devices. The rest of the directory structure is delimited by a single dot.
The next thing you may have noticed is that my example file called
Pi
has no extension! How do you know
this is a text file, I hear you ask? Recall that RISC OS is based around a WIMP user interface and this interface uses
something inside every file called metadata. Metadata are information about a file that is saved with the file. The
metadata are set on a per-file basis and the WIMP interface reads the attributes. Once it has read the metadata for file
type it will change the icon of the file. This is how you know it's a text file; the icon will be of a text file and a zip file has
a little zipper on it and so forth. It's all part of the way a WIMP interface works. Take a look at Figure
11-3
where you
can see how I have set the file type metadata on an application file.
