But First, a Little History

But First, a Little History

"What we wanted to preserve was not just a good environment in which to do programming, but a system around which a fellowship could form. We knew from experience that the essence of communal computing, as supplied by remote-access, time-shared machines, is not just to type programs into a terminal instead of a keypunch, but to encourage close communication.

Dennis M. Ritchie, coinventor of Unix, from "The Evolution of the Unix Time-Sharing System,"
AT&T Bell Laboratories
Technical Journal 63, No. 6, Part 2, October 1984
(http://cm.bell-labs.com/cm/cs/who/dmr/hist.html)

How did Unix end up as the underpinning of the Mac OS? In 1997, after a series of unsuccessful attempts to update the Macintosh operating systemremember Pink and Copland?Apple bought NeXT, the computer company that Apple cofounder Steve Jobs had started 12 years earlier after he was forced out of Apple. NeXT had developed a powerful operating system with an elegant user interface, but it had failed to become commercially successful. (Of course, commercial success is not the only way to gauge the quality of a product. None other than Tim Berners-Lee, inventor of the World Wide Web, used a NeXT machine for his development work on hypertext.)

When Apple bought NeXT, it got the code for NeXT's operating system, development tools, and user interface. But, more important, it got Steve Jobs and a culture of Unix-based development. The NeXT operating system (called NextStep), while largely written from scratch, was a version of Unix, and the NeXT engineers were used to a Unix culturethat is, employing powerful, flexible tools and systems in an environment of creative engineering. Given the effect on Apple's operating-system development, some people say that, culturally, NeXT bought Apple.

Mac OS X is based on a new version of Unix called Darwin. Darwin is a direct descendant of the Unix technology underlying NextStep, yet virtually every component has been significantly upgraded by a massive infusion of new open -source software, as well as some significant Apple-specific innovations. The cultural influence of NeXT and the software itself played a huge part in moving Apple toward the values of openness, flexibility, and stability.

Where did those values come from? They were part of Unix from its beginnings. Unix was born in 1969 from the efforts of a small group of scientists working at AT&T's Bell Labs to create an operating system that would allow the group to continue the kind of collaborative programming it had been doing on an earlier project called Multics. Thus, from the very beginning, Unix was conceived as both a multiuser and multitasking systemthat is, one that many people and many programs could use simultaneously and harmoniously.

Unix Pioneer: Bill Joy

Perhaps most recognizable to the general population as the chief scientist and cofounder of Sun Microsystems, Bill Joy is known in the Unix community as the primary designer of the Berkeley Software Distribution (BSD) version of Unix.

Among Joy's many contributions are the NFS (Network File System) protocol, the open-source version of TCP/IP, and the vi text editor.

After BSD Unix's introduction in 1983, it became the first widely distributed open-source version of Unix and has been the basis for numerous later versions of Unix, including Darwin, the core of Mac OS X.

More information about Bill Joy is available at www.answers.com/topic/bill-joy.

In the late 1970s, the University of California, Berkeley, used Unix extensively in its computer science department, several of whose members contributed features to the operating system. A key contribution: building in support for TCP/IP (the networking protocol suite that defines the Internet), added in the early 1980s. Virtually all current versions of Unix use the Berkeley networking code or its derivatives. Eventually, the version of Unix that came out of the university was dubbed the Berkeley Software Distribution (BSD). The Darwin layer of Mac OS X is directly based on BSD along with NextStep (mentioned above). As with Linux, you can run Darwin by itself on many hardware platforms (including the Intel architecture); however, it won't look like Mac OS X without the proprietary components Apple provides in Mac OS X.

Think of Mac OS X as having several layers : The bottom, or foundation, layer is Darwin ( Figure 1.1 ). On top of Darwin are a number of proprietary software components that Apple has added. Above it all is the layer that users seethe graphical interface called Aqua. You can use Mac OS X for traditional Macintosh tasks without ever being aware of the layers underneath Aqua, including Darwin.

Figure 1.1. Apple built the latest version of its operating system, Mac OS X, on top of a version of Unix called Darwin. Between the Aqua interface and the underlying operating system are Apple-specific layers.

Unix Pioneer: Linus Torvalds

Linus Torvalds is widely known as the inventor of Linux, a completely open-source Unix-like operating system. Torvalds wrote the core of Linux, called the kernel , and released the first version in 1991.

Besides the Linux kernel, Torvalds's most significant contribution to Unix has been his ability to gently and productively facilitate and coordinate the efforts of literally hundreds of programmers whose work makes up the current version of the Linux kernel.

Torvalds made a key decision when he released the code for the Linux kernel under a software license called the GNU General Public License (GNU GPL), which requires anyone making changes to the source code to make those changes freely available to the world. Most installed versions of Linux come with hundreds of other pieces of software also licensed under the GNU GPL, and so the name GNU/Linux is usually more accurate when speaking of Linux.

More information about Linus Torvalds is available at www.answers.com/topic/linus-torvalds.

Torvalds's own homepage is at www.cs.helsinki.fi/u/torvalds.

Beyond Unix: Other Open Systems

Mac OS X includes many open-source technologies that are also helping to revolutionize the information infrastructure of society.

• HTML The ease of creating documents using Hypertext Markup Language drove the growth of the Web. Anyone viewing a Web page can see, copy, and modify the underlying HTML. The HTML standard is coordinated by the World Wide Web Consortium (www.w3c.org/MarkUp/).

• Apache Web server (http://httpd.apache.org) By far the most popular Web server in the world, Apache provides a huge variety of configuration options and can be altered easily to add new ones. Mac OS X comes with Apache (see Chapter 14, "Installing and Configuring Servers").

• Perl (www.perl.org) This powerful scripting and programming language (which comes with Mac OS X) is used in scripts as short as 20 lines and in large object-oriented applications with thousands of lines of code.

• C The programs listed here and those included in every version of Unix are writtenwith few exceptionsentirely in the C programming language. To learn more, check out The C Programming Language , Second Edition, by Brian W. Kernighan and Dennis M. Ritchie (Prentice Hall, 1998; http://cm.bell-labs.com/cm/cs/cbook)the fundamental book on the topicor "The Development of the C Language" (http://cm.bell-labs.com/cm/cs/who/dmr/chist.html).

• SSH The Secure Shell tool facilitates secure connections between computers. The open-source version is maintained by the OpenBSD project (www.openssh.org).

• GCC The GNU Compiler Collection translates programming source code into machine-executable applications. It's maintained by the Free Software Foundation (www.gnu.org/software/gcc/gcc.html).

• Postfix and Sendmail (www.postfix.org and www.sendmail.org) Mac OS X comes with both of these common mail-server software applications, which you can use to set up your Mac OS X computer to be your own mail server.

Apple not only utilizes these open technologies, but also submits improvements to these and other open-source technologies so that other open-source users benefit, even if they are not using Mac OS Xopen source is not only taking, but also giving back to the community.

Unix Pioneer: Dennis M. Ritchie

Dennis M. Ritchie has been a computer scientist with Bell Labs for 35 years. He is most famous for having assisted Ken Thompson in inventing Unix and for being the primary creator of the C programming language (with Brian Kernighan in 1972). Ritchie is also a parent of another operating system, called Plan 9, that is well-known to the community of people who develop operating systems. He is currently head of the System Software Research Department at Bell Labs, where he helped develop a new operating system called Inferno and currently manages a group of researchers.

Dennis M. Ritchie's homepage: www.cs.bell-labs.com/who/dmr.

Unix History Timeline

Some key dates in the development of different Unix versions:

• 1970 Ken Thompson suggests the name Unix for the fledging operating system born in 1969 at AT&T Bell Labs.

• 1973 The kernel (core) of Unix is rewritten in the C language, making it the world's first operating system that's "portable"that is, able to run on multiple kinds of hardware.

• 1977 First BSD (Berkeley Software Distribution) version is released. Licensees must also get a license from AT&T.

• 1983 Version 4.2 BSD is released. By the end of 1994, more than 1000 licenses are issued. AT&T releases its commercial version, System V.

• 1983 AT&T releases System V release 3. IBM, Hewlett-Packard, and others base their own Unix-like systems on this version.

• 1989 NeXT releases NextStep which includes an operating system based on 4.3 BSD as well as a sophisticated graphical user interface and well-regarded set of tools for developers. Ten years later Apple will release revised versions of much of NextStep as Mac OS X.

• 1991 Linus Torvalds releases version 0.02 of Linux, an open-source, Unix-like operating system.

• 1992 Bill Jolitz releases 386/BSD, a full version of Unix with no AT&T code.

• 1992 Sun Microsystems releases Solaris, a version of Unix based on System V release 4, incorporating many BSD features.

• 1994 BSD4.4-Lite is released by the University of California, Berkeley. It is entirely free of legal encumbrances from the old AT&T code. Version 1.0 of Linux is also released this year; Linux incorporates features from both AT&T's System V and BSD versions of Unix.

• 1999 Apple Computer releases Darwina version of BSD Unix and the core of the Mac OS X.

For More on Unix History

• CrackMonkey (http://crackmonkey.org/unix.html) A history of Unix, including a discussion of its important flavors.

• The Evolution of the Unix Time-Sharing System (http://cm.bell-labs.com/cm/cs/who/dmr/hist.html) Coinventor Dennis M. Ritchie offers a technical and social history of Unix.

• "Overview of the GNU Project" (www.gnu.org/gnu/gnu-history.html) A history of the Free Software Foundation's efforts to create an open and free version of Unix.

• Open Source: Darwin (http://developer.apple.com/darwin) Apple's official Darwin Project site, where you can download source code and find links to other related projects.

• OpenDarwin.org (http://opendarwin.org) General-purpose site about Darwin, including links to mailing lists.

• The GNU-Darwin Distribution (http://gnu-darwin. sourceforge .net) Web site that "aims to be the most free Darwin-based Unix distribution."