"Last year Mac OS X was a promise. This year, it's a reality." Well, almost. According to sources, the words that appear on ads for next week's Apple Worldwide Developers Conference in San Jose, California, are mostly true. These sources told ZDNet that Apple is rushing to deliver a full beta of Mac OS X, its next-generation operating system, to developers at this year's gathering. This beta will include a revised interface that folds in more-traditional Mac OS elements while boosting basic features (such as printing) and new technologies that were not implemented in earlier developer previews. The company has pledged to deliver the final version of Mac OS X this summer; observers are predicting that means July's Macworld Expo in New York. Sources said the planned beta will closely resemble Developer Preview 4 of the OS, which the company reportedly distributed to members of Apple's Developer Connection in late April. According to sources, that prerelease version adds more familiar interface elements to the candy-colour Aqua interface that Jobs unveiled at January's Macworld Expo in San Francisco. Aqua's radical departures from the established Mac interface -- which was based on the long-term work of interface engineers and codified in Apple's Human Interface Guidelines -- drew the ire of some Mac loyalists and interface designers, who accused the company of abandoning navigation and work-flow considerations in favour of visual glitz. One of the most-criticised elements of Aqua was the Dock, a catch-all area at the bottom of the screen that contains icons representing minimised files and windows, active applications, favorite applications that have not been launched, the trash and other elements. Critics complained that the Dock tried to replace too many disparate functions, such as a launcher, application switcher and window manager. Some of the complaints seem to have reached Cupertino: In DP4's Dock, according to sources, the left side of the Dock is reserved for active applications, providing some separation from minimised windows and shortcuts, which are located on the right. The desktop has also received some Mac-style enhancements, sources said, including an option for showing mounted disks either on the Desktop or within the Dock. In earlier revs, these disks (including removable media) would not automatically appear, much as they don't in Windows. Users would have to open a "Computer" directory to see if a disk was available. DP4 also cleaves more closely to the Mac model with its default and optional dragging behaviours than did previous versions. In Jobs' Macworld Expo demo, he showed that dragging a file resulted in a copy of the file being made in the target directory -- standard for some Unix systems, but different from Macs, where dragging moves an item wholesale. Moving was accomplished by dragging an item with a modifier key held down. This scheme has reportedly been switched around to the Mac standard: The default dragging behaviour involves moving an item and dragging with the Option key producing a copy. DP4 also introduces new features and capabilities that should be part of the upcoming beta, sources said. One feature would address problems with Mac OS X's support of multiple file systems. Previous Mac OSes have used HFS and Extended HFS for managing files; Mac OS X's native system, however, is UFS, inherited from the OS' progenitor, OpenStep. The systems handle information about the file differently, and, in the past, files created in one required destructive conversion before being usable in the other. However, sources said Mac OS X will automatically save the "fork data" from HFS and Extended HFS files (all files operating in Mac OS X's "classic" and Carbon environments) when they are moved to a native Mac OS X directory. These files would then be able to be moved back with no loss of data or functionality. New rules for printing DP4 also features PrintCenter, which Apple documentation calls a "a totally rewritten printing architecture." (Previous versions did not support printing at all.) According to sources, PrintCenter acts as a central application for queuing and monitoring print jobs as well as selecting printers on a desktop system or over a local network. It is designed to replace the Chooser application in the current Mac OS. However, this new software doesn't mean all DP4 users will be able to print just yet. PrintCenter, according to sources, will only support printers that use the PostScript printing language. In addition, sources said, the documents indicate that Apple-developed printer drivers that will ship with Mac OS X will only support the legacy population of Apple-branded PostScript printers. "Third-party developers (such as Epson, Canon, Hewlett Packard, etc.) will have to create new printer drivers for their PostScript printers in order to use the new printing architecture to communicate correctly to the PrintCenter," according to the document. In addition, Mac OS X will reportedly only support laser or inkjet printers bearing Universal Serial Bus or Ethernet (TCP/IP and AppleTalk) interfaces. "PrintCenter is a newly designed printing architecture and, as such, does not support older printer types that connect to computers through obsolete input/output ports," the document said. "This would include SCSI, serial and infrared. This should be fine for Mac OS X Client, as it is only supported on Apple G3 and G4 computers which in great majority do not come with SCSI, serial or infrared ports. The three exceptions are the original Desktop G3 Beige, G3 All-in-One, and original PowerBook G3 systems, which all included a serial port. The PowerBook also has an Infrared port. Those computers will have to connect to a printer through the Ethernet port." According to sources, both DP4 and the upcoming beta will offer more-solid support for symmetric multiprocessing (SMP) through the latest revision of the Unix-based Mach kernel, the underlying core of Mac OS X. (SMP is the capability of an operating system to schedule and integrate tasks among more than one processor.) Apple has not made a multiprocessor system since mid-1997. The report that Apple will demonstrate the multiprocessor capabilities of Mac OS X at WWDC lends credence to speculation that the show will mark the debut of a rumoured multi-G4 desktop system code-named Mystic. Apple did not immediately return telephone calls requesting comment Chris Long is at it again. Last time he was having a go at the Mac community. Not content with doing it once he's gone for the double whammy this time -- swooping in to put us right about Macs again and then politely informing us that ADSL is not necessarily going be a good thing. Whatever next? What do you think? Tell the Mailroom. And read what others have said.