Chapter 1. Welcome to Mac OS X

1. Welcome to Mac OS X

IN THIS CHAPTER

The Heritage of Mac OS X: UNIX	2
The Open Source Connection	3
The Mach Kernel	3
The GNU Project	4
The BSD UNIX System	5
Darwin	5
Standards	11

Mac OS X (The "X" is pronounced "ten") is the descendant of two operating systems: the classic Mac OS and the NeXTSTEP operating system. Mac OS X is much more closely related to NeXTSTEP, even though the application environment and user interface are more familiar to Macintosh users. This chapter begins by providing a brief history of Mac OS X; the rest of the chapter fills in some of the details.

The Mac OS debuted in 1984 as a single-tasking system. The first multitasking support appeared in Mac OS 7 (called System 7, not related to UNIX Version 7), released in 1990. By the time Mac OS 8 and 9 came out, the writing was on the wall: Mac OS needed to be revamped. In fact, discussions of the upcoming new operating system occupied Mac advocates and debaters for many happy years, starting shortly after Mac OS 7 was released. Some of the technology and application program interfaces (APIs, page 921) developed for the planned new system were supported under Mac OS 8 and 9. They became the Carbon interface, used to provide compatibility between classic Mac OS and Mac OS X.

Meanwhile, in the late 1980s, Steve Jobs began developing a computer that was similar to the Mac in many ways, named the NeXT. The NeXT was generally regarded as technically brilliant but too expensive and too slow. The first systems, which were released in 1988, used special removable optical media drives instead of conventional hard disks. The NeXT platform, called NeXTSTEP (with varying capitalization from one year to the next), was one of the first adopters of the Mach (pronounced "maak") microkernel developed at Carnegie Mellon University (CMU) in the mid-1980s. The NeXT used BSD UNIX tools and utilities, and it offered a BSD UNIX API for developers. The NeXT also had its own development environment, based on Objective-C, which was built around the GNU C compiler and GNU development tools The system also used some GNU utilities. NEXTSTEP (with the capitalization changed yet again) was the basis for a new API named OpenStep, which was shared with Sun. The OPENSTEP system (NeXT's implementation of the OpenStep API) became the new NeXT platform.

In 1996 Apple hired Steve Jobs as CEO, and in 1997 Apple bought NeXT. The various attempts to redesign Mac OS were over: The NeXT operating system was to become the new operating system for the Macintosh. Mac OS X was first released commercially in 1999, when Mac OS X Server hit the market. The first retail release of Mac OS X aimed at end users was in early 2001, but it was not until late 2001 that the system was stable enough for widespread adoption.

Mac OS X release 10.4 is still based on the Mach microkernel, the GNU development tools, the BSD UNIX utilities and API, and recognizable pieces of the NeXT user interface. The UNIX utilities have been updated from 4.3BSD to 4.4BSD, with pieces of NetBSD, FreeBSD, and 4.4BSD-Lite release 2 added. Today, Mac OS X mostly tracks FreeBSD's utilities and libraries.

Several major releases of Mac OS X have occurred, each with the code name of some large feline. In order, they are 10.0 (Cheetah), 10.1 (Puma), 10.2 (Jaguar), 10.3 (Panther), and 10.4 (Tiger). Two versions of Mac OS X are available: Mac OS X and Mac OS X Server.

The Darwin system, which is the foundation for Mac OS X, has version numbers that correspond to Mac OS X version numbers. Mac OS X 10.3 is based on Darwin 7.0, and Mac OS X 10.4 is based on Darwin 8.0. Minor version numbers follow a similar pattern: Darwin 8.2 code is used in Mac OS X 10.4.2.