When you open a file, the application that's designated as the
file's preferred application displays the file's contents. However,
there are times when you may want to use some other application
to open the file. Zeta keeps track of all applications capable of
handling the file type. These applications are called candidate
applications. To get a list of all candidate applications for a
file type, select one, right-click it with the mouse and choose
the Open With command in the File menu. An Open With
window is displayed that shows all the applications the system thinks
it can use to open the file.
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The applications are divided into four "relations," by
their aptness for opening the file:
- The first relation always contains the preferred application
(only). This is the application that's used by default to open
the file.
- The second relation shows all applications that handle the
file's specific type. These "alternate" applications
are every bit as appropriate as the preferred application.
- The third relation shows applications that know how to handle
the file's generic type. Examples would be video applications
that open any MPEG file, or applications that open any type of
text file, whether the text is in a word processing file or source
code file.
- In the fourth relation are wildcard applications that will
try to open any file.
These selections are done according to MIME. Applications that
can handle the file's full type (e.g text/plain), applications
that can handle the file's supertype (text/...) and last
applications that can handle any file type (.../...). You
can read more about how Zeta uses MIME in Registrar.
If you select an application other than the preferred one, the
Open and Make Preferred button becomes live. This
button makes the application you choose the preferred application
to open this file and all other files of the same type. Selecting
an application in the list and choosing Open uses the chosen
application without changing the identity of the preferred application.
If the system can't identify the type of file you're trying to
open, the Open With window will list all applications,
and list as them as "Does not handle file." If you choose
one of these apps, an overly cautious dialog warns you that the
application you've selected to open your file doesn't support the
file.
You can also get to the Open With list by popping open a file's
context menu. The four relations are divided graphically:
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