"GM" in this instance stands for "gold master," a now-anachronistic term that refers to an era when software was burned onto master optical discs, sometimes gold-colored as a mark of archival durability, and to vinyl records before that. The GM seed will become the official commercial release if no show-stopping errors turn up.
OS X Mavericks follows the release of iOS 7, Apple's mobile operating system, last month -- timing that works well given the growing areas of overlap between the two operating systems. iOS 7 added AirDrop, a file-sharing mechanism introduced in OS X Lion, and OS X Mavericks adds Maps and iBooks from the iOS world. That's in addition to crossovers facilitated by iCloud with apps such as Notes and Reminders and common services like iTunes Radio.
There has long been speculation about whether OS X and iOS will converge. That could still happen at some point if Apple sees some advantage in doing so. For the moment, however, the two operating systems are merely cohabitating peacefully.
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OS X Mavericks doesn't bring dramatic changes to the Mac, but it does offer a lot of thoughtful improvements that add up. Here are 11 of the new features that might make it worth installing.
1. App Nap
App Nap isn't an application. It's a low-level power saving feature designed to throttle the energy used by apps that are running in the background. Apple claims it can reduce CPU energy usage by 23%. Anything that keeps your MacBook Air alive longer matters.
2. Sprite Kit
Game developers tend to use software frameworks to simplify the process of game creation. For those who have the skill to use Objective-C rather than higher-level cross-platform alternatives like Unity3D, Corona SDK or Platino, there are options like Cocos2D. But in OS X Mavericks, Apple is offering developers its own set of APIs for making 2D games: Sprite Kit. For the end user, that's likely to mean more quality games for the Mac, because Sprite Kit is also available in iOS, making it easier to create games that run on both of Apple's operating systems.
3. AV Kit
AV Kit is a set of media APIs for developers. With AV Kit, app makers should have an easier time creating apps that support media playback, with bells and whistles like navigation controls, chapter selection and subtitles.
4. Safari Power Saver
You can never have too much power when working unplugged. Like App Nap, Safari Power Saver strives to make sure you have the battery power you need. This browser technology is to Web media as occlusion culling is to 3-D graphics optimization: It prevents the processing of content that's hidden from view.