Datasheet

QuickTime movies. But QuickTime also makes most, if not all, of its functionality available to applica-
tions through its framework interface.
When you save a Slide Master document, the document file contains a list of image files that are part of
your slide show, not the actual images themselves. As a result, these documents can be relatively small.
Behind the scenes, Slide Master uses aliases to track these image files so that they can be found if the
files are moved around on your disk. These aliases are the same aliases you can create in the Finder,
although they are embedded in your document rather than saved separately to disk. Slide Master uses
the Carbon application framework for working with aliases. Even though Slide Master is a Cocoa appli-
cation, it can still access many of the services available in Carbon.
You learn more about Cocoa, Carbon, QuickTime, and other technologies later in this chapter, and as
you proceed through this book.
The Core Operating System
The heart of Mac OS X is based on the Unix operating system. Unix was developed by AT&T in the early
1970s. In those days, computers were large and expensive, and Unix was intended as a way to share
computing resources between multiple users at once. It was likely that an organization at that time could
afford only one computer for all its members, and Unix provided a way for people to use that computer
simultaneously without getting in each other’s way.
Over the years, Unix development has split off into many distinct “flavors” of Unix, all headed up by
different groups of people, all with somewhat different goals. BSD and Linux are two such examples.
Each version of Unix shares some portion of the original vision and typically implements a common set
of libraries and commands.
Unix is regarded as a robust operating system whose scalability and innate networking capability make
it ideal for use as a server. In fact, most of the modern day Internet is powered by Unix servers of one
version or another. It turns out that these features are also desirable in modern desktop operating sys-
tems. So it is no surprise when seeking to modernize the original Macintosh operating system, Apple
turned to Unix.
Mac OS X’s core operating system is a Unix flavor called Darwin. Like most Unix flavors, Darwin’s
source code is freely available, allowing interested parties to see exactly how the core operating system
works. Apple maintains several resources for programmers interested in Darwin, including a way for
people-at-large to contribute changes and bug fixes back to Apple.
Although Mac OS X tries to hide Darwin from the average user, there are some places where the Unix
command-line pokes through. The most obvious example is the Terminal application, found in
/Application/Utilities. You can use Terminal to work directly with Darwin’s command-line tools.
A more subtle example includes the way you describe file locations on Mac OS X: by using a file path. A
file path is a string of text that describes a file’s location.
The original Mac OS operating system abhorred file paths and tried its best to avoid them; but even so it
devised a convention for describing a path to a file. Mac OS file paths are composed of a disk volume
name followed by several folder names and possibly a file, all separated by colons, as in
Macintosh
HD:Applications:Utilities:Terminal.app
.
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