If a voice inquiry, Siri invokes a speech-to-text mechanism that transcribes what has been spoken to text. This is very difficult, by the way, particularly given the number of languages in which Siri works.

NEW YORK--Only a few years ago, the launch of a new computer operating system set off impassioned clashes between devotees of the Mac and supporters of Windows. Tuesday's arrival of macOS Sierra seems like an after-thought by comparison, coming with nowhere near the media attention that's paid to an iPhone or even iOS release. The marquee feature is Siri's debut on the Mac, and while this is mainly a welcome development, the fact is we all got to know Apple's loquacious personal assistant on the phone first. Indeed, with Sierra comes further evidence that we're fully entrenched in a post-PC world, where the computers in our pockets have trumped those on our desks. Microsoft with Windows 10 has for the most part designed a single operating system that is meant to work across PCs, phones, tablets, even Xboxes.

In summer 2014, Apple completely changed how Siri works. The secretive Cupertino, California, company adapted Siri's voice recognition to use a cutting-edge artificial-intelligence technique called neural networks and switched it over on July 30, 2014, according to an in-depth feature by Steven Levy of Backchannel. Neural networks is a type of AI inspired by the human brain that has become especially useful thanks to today's powerful computers. Before that, Siri recognized human voices using more rudimentary AI techniques that have been around for decades. It was the biggest change to Siri since it launched in 2011.