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Ten: In The Beginning There Was Darwin, And The Open Source Community
Said It Was Good - An Overview Of Darwin And Quartz
Darwin
The open source core of Mac OS X is based on a Unix microkernel, consisting of the Mach 3 microkernel and FreeBSD 3.2. The Apache Web server, which powers a majority of Web sites, has been tamed and forms the basis of the new operating system's file sharing capabilities.
NOTE: Apple's open source project, called Darwin, allows the core components of the operating system to be made available, free, to software developers, with Apple retaining full rights to the code. These developers can test and debug the software, then make available bug fixes and enhancements to the entire developer community. For more information about this feature, feel free to visit Apple's Darwin Web site, www.apple.com/darwin.
Although its Unix underpinnings are well hidden beneath Aqua's striking user interface, they are not invisible. Power users can easily pour beneath the surface, bypassing the graphical user interface, and run regular Unix-based applications under Mac OS X. Apple has even provided a Terminal application in the Utilities folder, so power users can visit the command line and access the core Unix functions. In addition, the new Mac operating system offers the very same industrial-strength features that are the hallmark of Unix. These include the following:
¡ Protected memory - Each program you run resides in its own address space, walled off from other programs. If a single program crashes, that application is shut down, along with the memory address space it occupies. You can continue to run your Mac without the need to restart. This will help to sharply reduce the Mac OS's tendency to crash at the least sign of a software conflict.
¡ Preemptive multitasking - Apple's previous multitasking method was cooperative, meaning that each application would, in effect, have to share CPU time with other programs. This meant that if you were working in a program, such as typing in a word processing document, background tasks, such as printing or downloading a file, could come almost to a screeching halt, particularly if a program hogs processor time unnecessarily. With Mac OS X, the operating system serves as the traffic cop, performing the task management. This allows programs to run more efficiently, and with fewer slowdowns when multiple processes are running.
¡ Advanced virtual memory - With previous versions of the Mac operating system, virtual memory meant slower performance, poor performance with multimedia programs, stuttering sounds, and other shortcomings. Under Mac OS X, virtual memory management is dynamic. Programs are automatically given the amount of memory they require, whether available via RAM or virtual memory disk swapping. Performance is optimized, so you get the maximum-possible performance from your programs.
NOTE: Virtual memory in Mac OS X is super-efficient, but it can't do miracles. There is no substitute for having sufficient RAM to run your high-energy programs, such as Adobe Photoshop or Apple's Final Cut Pro, to get the best possible performance. But you will no longer have to visit the Get Info window to keep changing a program's memory allocation to meet your needs
Quartz
In previous versions of the Mac OS, Apple used an imaging model called QuickDraw to generate pixels on your display. For Mac OS X, Apple has given up this technology, moving instead to Adobe's Portable Document Format (PDF). As you probably know, most electronic documents are available in PDF trim, which retains the exact formatting, fonts, pictures, and colors of the original.
There is full system-wide support for the major font formats - PostScript, TrueType, and the new OpenType format. That means that Adobe Type Manager (ATM) is no longer needed to render fonts crisply on the screen, although font management is not quite as extensive as the Deluxe version of ATM.
The Quartz 2D graphics system is extremely powerful, with speedy rendering of images and anti-aliasing, providing sharp screen display.
There's also system-level support for PDF, which makes it easy for Mac software developers to provide built-in support to save documents in this format. In addition to PDF, Apple includes support for ColorSync to ease color management from input to display to output; the industry-standard OpenGL, which provides superlative performance for many 3D games; and Apple's famous QuickTime, used worldwide for generating multimedia content.
For more information on OS X visit MacSpeedZone's X-Files
The article above is excerpted from the book "Mac
OS X Little black Book" by Gene Steinberg
Copyright 2001 The
Coriolis Group.All rights reserved.
Reproduced here by permission of the publisher
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