Watch out, Siri. Someone wants your job. Since its debut on the iPhone 4S three years ago, Apple's Siri technology has been synonymous with the concept of a virtual personal assistant. But now comes Cortana, an intelligent assistant from Microsoft that's supposed to be much like Siri, only better.

Watch out, Siri. Someone wants your job.

Since its debut on the iPhone 4S three years ago, Apple�s Siri technology has been synonymous with the concept of a virtual personal assistant. But now comes Cortana, an intelligent assistant from Microsoft that�s supposed to be much like Siri, only better.

Cortana is one of the key features of Windows Phone 8.1, the latest update to Microsoft�s smartphone software that is beginning to show up in new devices. The feature is something like a combination of Siri and Google Now, the intelligent-assistant technology built into Android.

Like Siri, Cortana can send text messages, search for information on the Web and launch applications in response to users� inquiries and statements. As with Siri, users generally don�t need to use specific commands but can talk naturally, as if they were speaking to a real person.

But unlike Siri, Cortana also can act like Google Now, providing information unprompted by a particular inquiry. Looking at your calendar, Cortana can tell you when you need to leave for an event to make it on time. And by knowing your favorite sports team, it can keep you updated on the results of its latest games without you asking for the score.

Microsoft has designed Cortana so that individual users can customize it to a much greater degree than they can Siri or Google Now. Inside a settings area, users can view and edit the information Cortana knows about them, such as the name of their spouse or their office address.

Cortana, which, like Siri, allows you to assign it either a male or female voice, also knows some pretty cool tricks. Like Google Now, but unlike Siri, Cortana shows what it hears you saying as you speak. This feedback can reassure you that Cortana is listening and understands what you are saying.

As with Siri, you can use Cortana to set reminders and can specify that you want to be reminded to do them at a particular time or when you arrive at a specific place. But Cortana also can remind you to do things when you interact with particular people.

So you can ask Cortana to remind you to wish your mother a happy anniversary the next time you talk to her. Then when you send a text to your mother or receive a call from her, Cortana will flash a message on the screen reminding you about the anniversary.

With reminders, Cortana tends to be more inquisitive than Siri. Cortana will ask what time you want to be reminded. And if you want to be reminded of something when you go to a store, say Trader Joe�s, it will ask you which Trader Joe�s location you mean.

With Siri, you have to remember to tell it that you want to be reminded at a particular time. And Siri was baffled when I said I wanted to be reminded when I got to Trader Joe�s.

Microsoft is also allowing app developers to create custom commands for Cortana, something that Apple does not allow for Siri.

By contrast, Siri recognizes only the commands that Apple has plugged into it. Apple hasn�t yet allowed app developers to tap into Siri other than for dictation. Over time, Cortana�s openness could give it the ability to do a lot more things than Siri can.

But for now, Siri is a lot more capable personal assistant than is Cortana. Either will help me find nearby restaurants, but only Siri will make a reservation for me. Cortana, at best, will direct me to the OpenTable app.

If I tell Siri I want to see a movie, it will list show times at local theaters and even let me buy tickets. Tell Cortana the same thing, and it will simply do a Web search on the movie title.

There are other things that Cortana can�t yet do that Siri can. It can�t set a timer, nor can it post updates to Facebook or Twitter, or send an email message.

The feature also has a two-step launching process. That might not seem like much, but it�s one or two button presses more than you need with competing assistants. You can activate Siri with only a long press of the iPhone�s home button. And on Motorola�s Moto X, you can launch Google Now by just saying �OK Google Now,� with no button press required.

Cortana has the potential to be a very capable personal assistant in the not-too-distant future. But I wouldn�t fire Siri just yet.

Troy Wolverton is a technology columnist for the San Jose (Calif.) Mercury News.