Cortana is present primarily as a search bar under the Start menu; you can also launch it by tapping its tile on the Start menu. (In tablet mode, it's accessible from an icon on the Taskbar). You wake it up by saying "Hey Cortana" or "Hi Cortana." You can then ask it to do something, such as find a file, launch a program or find information. If you prefer typing to talking, type your request into the search bar.
What you'll see next depends upon your request. Cortana, which is based on Bing's search engine, looks through your files, your Microsoft OneDrive cloud storage account, your videos and music, the apps on your PC, your settings, your email and the Web. The actions it takes or the way it shows your search results varies according to what you've asked for.
For example, when I said, "Show me my photos from Italy," Cortana quickly found them on both my PC and on OneDrive -- and displayed them. At the top of the results, I could click a link to search for photos of Italy on the Web.
When I asked, "What's the weather?" it knew my location and told me it was 74 degrees and sunny, and also displayed the weather forecast. And when I said, "Add an appointment on Sunday," it asked me what time the appointment was scheduled to start, and from there I was able to quickly add an appointment to my calendar.
There are limits to Cortana's capabilities, though. I use Gmail as my primary email account, and Cortana wasn't able to reach into it to search through messages. In fact, it wouldn't even launch Gmail for me. Instead, it did a Bing search for Gmail and showed me a page of search results on the Web. If Cortana is going to become a truly useful digital assistant, Microsoft will have to figure out a way for Cortana to interact with all the major Web-based apps.
I will say this for Cortana, though -- it's a fast learner. When I said "Launch Google Chrome," it asked whether I wanted to launch Google Chrome or Chrome App Launcher. I told it to launch Google Chrome. Every time after that, when I made that same request, it launched Google Chrome without asking for clarification.
When Cortana runs, it displays a menu made up of a group of four icons stacked underneath a "hamburger" menu on the left side of the screen, which are both somewhat useful and somewhat confusing. The top one, Home, simply navigates you to the main Cortana interface. Beneath it, the strangely-named Notebook icon leads you to a tool to change Cortana's settings -- such as whether you want to get recommendations about places to eat or events to attend; what your home, work and other "favorite locations" are; how to change the name Cortana uses for you; and so on.
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