Mac fans won't walk out of January's Macworld Expo/San Francisco with copies of Mac OS X 1.0 in hand, sources told ZDNet News, but they will leave Apple chief executive Steve Jobs' keynote address with a firm ship date for the next-generation OS. Apple's top brass expects to launch Mac OS X at a special event on Feb. 24, more than five weeks after Macworld Expo/San Francisco. That date is the last day of Macworld Expo/Tokyo, which kicks off 22 February, although sources said the Mac OS X rollout would not be tied directly to events at the Mac gathering in Chiba, Japan. Apple executives reportedly had hoped to have the final version of the first commercial release of OS X ready for the biannual Mac-centric conference, but that proved to be impossible. Instead, Apple chief executive Steve Jobs will use the San Francisco expo to make a formal product announcement that includes the final ship date. Currently, sources said, OS X has passed the "feature-complete" stage of development; the remaining work consists of bug removal and optimisation. That doesn't mean work on the operating system will come to a halt on the shipping date; there is expected to be an update to OS X, code-named "Orient," within three to 12 months of the 1.0 release. Sources also said that the latest, feature-complete builds of OS X include the upcoming revision to the current Mac OS, OS 9.1 (code-named Fortissimo) as its Classic environment. This fixes the current incompatibility between early builds of that operating system and the OS X public beta. Top Apple executives, sources said, have asserted that recent slow sales of Apple hardware have primarily been a result of customers holding off purchases until OS X's release. As a result, they think that as soon as OS X is out, hardware sales will enjoy a revival. One top executive characterised this sentiment as a "gut feeling" in recent conversations with Apple staff. Either at OS X's launch or at the January announcement, Apple will begin a "massive" marketing push for the operating system, sources reported. The push will be similar to the campaign Apple ran to promote Mac OS 8 in 1997. As part of this promotion, sources said, Apple is considering offering free OS X updates to those who purchase Mac systems at January's Macworld Expo or after. Also being considered by Apple executives, according to sources, is a plan to load OS X as the default operating system on the company's professional-level systems. Not releasing in January might "not necessarily" be a bad thing, said Tim Bajarin, a senior analyst at Creative Strategies. "It needs to come out with no bugs," Bajarin said. He also emphasised that quality, rather than a ship date, would make or break the OS in terms of acceptance by the Mac market. As for whether the fact that OS X's absence from the market has depressed sales of Mac systems, Bajarin said that was "not necessarily" the case. "What hurt Apple was overestimating demand for the Power Mac Cube and underestimating the need for a totally refreshed iMac line for this Christmas," Bajarin said. Apple began development of OS X soon after its December 1996 acquisition of NeXT Software -- the software and hardware company founded by Steve Jobs after his 1985 ouster from Apple -- and NeXT's advanced, object-oriented operating system, OpenStep. The goal of using OpenStep as the basis for a new operating system was to provide advanced capabilities such as fully protected memory, pre-emptive multitasking, and more, features that were targets for Apple's previous (and abortive) OS project, code-named Copland. Originally, the combination of OpenStep and the Mac OS was code-named Rhapsody; early schedules had developer versions of Rhapsody set for mid-1997, with general release of Rhapsody both with and without a Mac OS compatibility layer (then called Blue Box) in early and mid-1998, respectively. However, the project proved to be more difficult than originally conceived, both technically and politically. Apple's original strategy was to require developers to rewrite applications completely to a new development environment, named Cocoa. This was met with widespread resistance by both major and minor software companies. This impasse prompted Apple to create another, more familiar application environment, Carbon, that was a streamlined version of the existing Mac OS application programming interfaces. With Carbon, developers could modify their products to run in both the existing Mac OS and the next-generation system. Previous, un-Carbonised applications would run in the Classic environment, which was similar to a transparent Mac OS emulator. Classic applications, unlike Carbonised ones, would not take advantage of OS X's advanced features. By 1998, Apple's revised roadmap featured a preview version of the new operating system -- now called Mac OS X -- slated in late 1999, with a full release by mid-2000. This date also proved optimistic (much like Microsoft's multiyear quest to release Windows NT 5, which was later renamed Windows 2000). In 1999 and early 2000, Apple instead seeded feature (and interface) incomplete "Developer Preview" versions of OS X, which served primarily as technology demos for developers. In that time period Apple also shipped Mac OS X Server as a commercial product. Mac OS X Server was a hybrid of Mac and OpenStep features that lacked Mac OS X's Aqua interface and took aim at administrators of Web and file servers. It included many server-centric tools but was of limited use as a desktop operating system. Apple has been terse about its delivery plans for the client version of Mac OS X. Many observers expected May's Worldwide Developers Conference (WWDC) in San Jose, California, to see a release of a public beta of OS X, but instead Jobs distributed the Developer Preview 4 version of the OS to attendees. In his WWDC keynote speech, Jobs stated that a public beta of OS X would ship in the summer of 2000, with a final version "available for pre-install" on new Mac systems beginning in January 2001. This scheme represented a change from previous public statements (and Apple press releases) promising earlier delivery dates. The public beta arrived in early September 2000 at the Apple Expo conference in Paris. The OS X beta featured a revised version of the controversial Aqua interface and included changes made in response to vocal criticisms that had arisen since Jobs unveiled the GUI in January 2000. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.