Normally, if you wanted to use the same app on your iPhone and your Mac, you had to buy separate versions for each device. But now, Apple is helping app developers create one app for all devices. Instead of buying a copy of, say, Photoshop for iPad and one for your Mac, you can buy the app once and then install it on every iOS, macOS, iPadOS, or tvOS device you own.

In the announcement, Apple says: "Starting in March 2020, you can distribute iOS, iPadOS, macOS, and tvOS versions of your app as a Universal Purchase, allowing customers to enjoy your app and in-app purchases across platforms with just one purchase. You can choose to create a new app for these platforms using a single app record in App Store Connect or add platforms to your existing app record. Get started by building and testing your apps using a single bundle ID with Xcode 11.4 beta."

Xcode is used by Apple developers to create apps for Mac, iPhone, iPad, Apple Watch (not mentioned in Apple's announcement), and Apple TV.

In addition to developing what Apple calls Universal Apps (a term that previously only referred to apps you could use on your iPhone and iPad), the new Xcode will bring unified features across the Mac and iOS App Store categories. Developer Tools and Graphics & Design now come to iOS, while Books, Food & Drink, Magazines & Newspapers, Navigation, and Shopping are coming to the Mac App Store.