One of the big ideas underlying Microsoft’s new Windows 10 operating system is “universal” apps, meaning the same version can run on a personal computer, tablet and smartphone — no separate version is required for each gadget.

That is a great hook to spur a proliferation of apps for Windows 10-based devices. But since the operating system’s release in late July, apps built for the software have not exactly taken off. That could be because the mobile version of Windows 10 for phones and smaller tablets — which ought to prompt wider adoption of the operating system — is not yet available, though you can download a preview edition to test on your phone.

On the positive side, some “full” Windows 10 apps for bigger tablets have already appeared, as well as some mobile-ready universal apps that demonstrate the future of the operating system.

Those include WolframAlpha, a universal Windows 10 app that can be thought of as an anti-Google. Instead of having to sift through Google search results for the information you need, Wolfram is preprogrammed with millions of facts and can calculate even more for you.

You type in a query, such as, “How many days between July 28, 1914, and Nov. 11, 1918?” (the start and end dates of World War I), and the results appear with different levels of detail — telling you that the war lasted 1,567 days, or 4.49 years, for instance. There are icons for categories like physics or art and design, and tapping them brings up the kinds of questions you can ask. Some may surprise you, like “last M.L.B. game with more than 10 stolen bases.”

There is also something about the user interface design of Windows 10 that makes the $3 app look slicker on it than on iOS or Android.

Adobe has released a universal Photoshop Express app for photos snapped on your Windows 10 device. It uses touch and gesture controls, and does a good job of letting you add special effect filters, adjust image features (like how “noisy” the photo is) and change the contrast. These tweaks are made by dragging on-screen sliders to see the effect in real time.

Like WolframAlpha, the Photoshop interface feels at home in the Windows environment, and it is easy to navigate. But those hoping for the full Photoshop experience may be disappointed: The free app is for basic photo editing only and has a limited range of features. You can buy additional capabilities, such as the noise-reduction system and Instagram-like image filters, but these cost a few dollars via in-app purchase.

Twitter has a universal Windows 10 app that demonstrates some of the issues that Microsoft faces. Twitter works on Windows 10 much as it does on other devices: You can read tweets from other people in your timeline and share your own posts, including photos and videos.

But the strong design elements that characterize Windows 10’s mobile interface are strange in this free app. Using Twitter on Windows 10 feels different from using it on the web or another smartphone. The whole tweeting experience is swamped with Microsoft’s look and feel.

Though this is admittedly a matter of personal taste, there is another issue: Twitter on Windows is not as full- featured as it is on iOS. It is also sometimes difficult to use, with icons in unexpected places. Such issues raise questions as to whether developers invest the same effort in Windows apps as they do in apps for other smartphones.

Foursquare also has a universal Windows 10 app that has made the transition from previous versions of Windows. The free app, which has changed in function over time, is now a destination for crowdsourced reviews of venues like cafes, and it works just as well on Windows 10 as on other devices.

Reviewers in the app store say the new version is visually confusing, however, and the dominating Microsoft user interface makes it easy to forget that you are reading a restaurant review in Foursquare as opposed to some other app.

Microsoft’s Office suite of business productivity apps is also available on Windows 10 (naturally). On your phone and smaller tablets, Word, Excel and other apps are free, though they require a free Microsoft account for Office 365 and they have less document-creation and editing power than you may be used to on your PC. If you want to edit or create documents on larger tablets using the free apps, you will have to pay for an Office 365 subscription, which can get expensive. A personal annual fee, for example, is $70 a year.

There are other Windows 10 apps for phones, like those from Netflix and USA Today (bothfree). More will arrive when the Windows 10 Mobile operating system is made widely available. Whether that will spur the creation of more apps, and entice more people to use them, remains to be seen.

Quick Call

Infltr is a new $2 iOS app that says it offers much more than the limited handful of special-effect photo filters that other apps contain. Infltr (the name is a conflation of “infinite filter”) says it makes five million different effects accessible through a touch and gesture interface, and the filters are applied before taking the shot. There is a bit of a learning curve, but it is fun.