Back in June, screen shots of an early Windows Phone operating system build leaked (via a Lumia phone allegedly purchased on eBay). At that time, next-to-no attention was paid to an app, listed as “zCortana,” that was on the phone. But that Cortana app (with the “z” indicating it was a test build) is central to what Microsoft is doing to compete with Apple’s Siri and Google Now. And Cortana is back in the news this week with passing mentions by those tracking what’s happening with Windows Phone as it moves toward the “Blue” release in the early part of 2014. Cortana takes its codename from Cortana, an artifically intelligent character in Microsoft’s Halo series who can learn and adapt. Cortana, Microsoft’s assistant technology, likewise will be able to learn and adapt, relying on machine-learning technology and the “Satori” knowledge repository powering Bing. Cortana will be more than just an app that lets users interact with their phones more naturally using voice commands. Cortana is core to the makeover of the entire “shell” — the core services and experience — of the future versions of Windows Phone, Windows and the Xbox One operating systems.