posted by Gavin Wraith on Wed 5th Jul 2006 17:44 UTC

"RISC OS, 2/3"

RISC OS Filing Systems

RISC OS does have a command line, but it is so vestigial that most users are probably unaware of its existence. Better to use a taskwindow, which gives a command line in a window. The RISC OS desktop provides an iconbar along the bottom of the screen. At the right hand end sit the icons of running tasks, and at the left the icons of filing systems. Its purpose is to provide permanent access to basic facilities when there are no windows open.

[Note about pictures: some icons are provided as standard: desktop furniture, icons for filing systems or filetypes, etc. However, they can all be replaced by the user's own designs, so two users' screenshots may well appear totally different.]

Filing system is an important RISC OS abstraction. Different machines may come with support for different filing systems, and in theory users can write their own. Various modules are provided which provide the basic services that a filing system may require, so that filing operations (loading, saving, renaming etc) present a uniform drag-and-drop aspect to the user. Above you see icons denoting filing systems for:

  • CD
  • Hard disc
  • Shared discs on my LAN
  • The memory stick I have just stuck into a USB port
  • Floppy
  • The Resources read-only drive
  • Memphis, a third party RAM drive
  • SparkFS, a third party archiving system

A file's full pathname must contain a prefix that specifies which filing system it belongs to.

RISC OS mice have three buttons. The middle one is used exclusively for popping up a context sensitive menu. No jumbo-jet-cockpit clutter of drop-down menu icons. Window real estate is too precious for that. The left button is used for selecting items or initiating actions. The right one is used for adjusting selections or for performing operations inverse to those of the left button. These are matters of convention, for the most part. Drag a window with the left button and it will pop to the front and move over the top of other windows. Drag it with the right button and it will move at its own level in the window stack, behind windows that are further to the front. Clicking in a text window to give it the input focus does NOT move it to the front of the window stack; click on the text window's titlebar to do that. These are just a couple of ways, out of hundreds, in which the RISC OS desktop differs from those of other operating systems.

A very important aspect of the RISC OS desktop is the consistency of its visual metaphor. A filer window depicts the contents of a directory. The icons in the window depict files or subdirectories. To save an object to a directory you must open the directory's window and drag the object's icon inside. This way of doing things (as opposed to dragging objects onto icons) has two advantages: first, a directory window is a target harder to miss than an icon, and second, you get visual confirmation of a successful save by seeing the object's icon appear in the window. You cannot open two windows onto the same directory. That would break the metaphor. For saving data, an application will pop up a dialog box with an icon, which you then drag into a directory window. The filer is like the ocean - all desktop applications swim in it - they do not have to provide their own depictions of where files are. The desktop itself is the representation of the filer. This gives the most radical difference in feel from other operating systems. The screen is there to provide space for the user to read information, so you may need lots of windows open simultaneously. Applications in RISC OS are supposed to cooperate with each other, and taking over the whole screen, or changing the graphics mode is rude, selfish behaviour. I wonder if there is a thesis waiting there - Social paradigms in operating systems?

Applications and Filetypes

Files in filing systems have a filetype. This is 12 bits of data that play much the same role as a filename extender in other operating systems but which in RISC OS are not part of a file's name. The icon used to depict a file in a directory window depends only on filetype. Some filetypes are provided as standard, others can be user defined. You can always change the filetype if convenient.

There are two sorts of directory. Plain directories and applications. An application is distinguished from a plain directory first of all by having a name starting with ! . It also differs in appearance and in what happens when you click on it. With a plain directory, clicking on it will open its window, with the left button leaving open the window it resides in, but with the right button closing the window it resides in (so if you want to travel down the directory hierarchy without cluttering the screen, use the right button). With an application, however, clicking on its icon will run it. You can open an application as if it were a plain directory by holding down a shift key when you click on it.

Table of contents
  1. "RISC OS, 1/3"
  2. "RISC OS, 2/3"
  3. "RISC OS, 3/3"
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