Chapter 1

� changing directory and file attributes;
� notifying changes;
� manipulating drives and volumes;
� peeking at file data without opening the file (used by some file format recognizers);
� adding and removing file systems;
� system functions to control and check the status of the server.
Refer to the SDK for more details.
13.3.2 The Current Directory
Most RFs-related functions are stateless – that is, the results of a function don't depend on
any functions previously called. That's why you can share CONE's RFs with other libraries
used by your application.
RFs has just one item of state: its current directory. When you open an RFs, usually its
current directory is set to c:\; which as discussed, will be hidden from users in UIQ and may
be just a ramdrive in some devices, or a flash-based drive in others. Indeed, c: is always an
internal read/write drive on Symbian OS phones. On the Psion Series 5, it was a RAM disk,
but on smartphones, it's a flash-based medium, which is (a) persistent with respect to taking
the battery out – something phone users do frequently – and (b) slower, especially when
handling reads and writes scattered over discontiguous sectors.
You can use SetSessionPath() to change the current directory used by an open RFs.
You can use SetDefaultPath() to change the initial current directory for all future RFs
objects. The current directory includes the drive as well as directory names. So, unlike DOS,
there is no concept of one current directory per drive.
If you manipulate or rely on the current directory, make sure you use your own RFs rather
than sharing one with other programs.
13.3.3 Drives, File Systems, and Media
Symbian OS supports at least three different media types:
� The ROM file system that is assigned to z: was built by the ROM builder and is clearly
read-only as far as Symbian OS programs are concerned.
� An internal read/write drive that is always assigned to c: On smart- phones and
communicators, this is a flash-based drive, with flash performance characteristics, on
which data persists when all power is removed. Historically (i.e. Series 5 and netBook),
the internal drive was a RAM drive, which had the benefit of being much faster, but
which needed battery power to maintain even when the device was switched off, and
whose entire contents would disappear when all power was removed (such devices had
a secondary backup power scheme such as a backup battery – e.g. Psion Series 5 – or
some reserved main battery power like the Psion Revo). Symbian OS takes enormous
care to ensure that a sector write is atomic (that is, it completes entirely, or it doesn't
complete at all). In turn, higher-level components such as STORE and DBMS use
formats and protocols that ensure failure to write to the media never results in a corrupt
file.
� Removable media such as CF, MMC, MemoryStick, Microdrive or SD cards, on which,
if present, the main drive is assigned to d:. Such technologies require little power to
read, but rather more power to write. As battery power drains, it may become
impossible to write to such a drive. Again, Symbian OS takes enormous care to ensure
that a sector write is atomic.