Information Technology Reference
In-Depth Information
coordinate the running of programs. Because this work has many
different components, alternative strategies have emerged to ac
complish it, each with its own priorities and perspectives. For ex
ample, Microsoft Windows, Macintosh OS 9.0, and Linux follow
their own approaches to each of the many tasks that operating sys
tems oversee. (Technically, in early 2000, Apple made a funda
mental shift in its Macintosh operating system when it released OS
X. Version 9 used its own approach to disk formatting, whereas
Macintosh OS X became Unix/Linux based. New Macintosh oper
ating systems largely are compatible with Linux, whereas previous
versions of the Macintosh and Linux operating systems followed a
different approach.)
These differences extend to the conventions regarding the loca
tion and format of disks and their directories. In particular, each
operating system follows its own convention about which sector(s)
are used for the main directory and what the format of a file entry
is in that directory. Thus, to read a directory, an operating system
goes to the appropriate sector, reads a sequence of bits and bytes of
data, and interprets those data based on the conventions for that
format. To read a different disk format, the operating system would
have to go to a different sector, and/or the bits and bytes read would
have to be interpreted in a different way.
In normal processing, an operating system would expect a disk
to conform to its specific format conventions. Thus, a Windows ma
chine would expect a disk to follow its format, a Macintosh would
expect a disk in Macintosh format, and a Linux or Unix machine
would expect a disk in that format. When a disk of another format
is used, therefore, an operating system cannot follow its normal ap
proach to make sense of the data. For this reason, the Windows op
erating system is unable to read a Macintosh or Linux disk.
In the case of a Macintosh or Linux machine, the same initial
confusion arises when a Windows disk is inserted. However, with
the widespread use of Windows, developers of Macintosh and
Linux decided that it would be useful for their machines to be able
to share disks with Windows users. Thus, when a Windows disk is
inserted into a Macintosh or Linux computer, the operating system
realizes that the format does not correspond to normal conventions
and then shifts modes to try reading the file in a Windows format.
This second effort allows Macintosh and Linux machines to read
Windows disks.
