All Holographic apps running on HoloLens are UWP application. The following illustration represents the app model state for an app running on Windows Universal Platform. If you are familiar with developing Windows Universal app, you must be familiar with this app state model. Till now, you may have experience in developing 2D Windows Universal app for desktops, tablets, or phones. Windows Universal app for HoloLens is one step ahead; now, you can develop not only 2D apps, but also 3D apps. In this book, we will focus only on 3D application development to realize the power of MR.

The following are the high-level steps for a Holographic app life cycle:

• Placement
• Launch
• Execute
• Terminate
• Remove

App Launch starts as soon as we place the app into the HoloLens Shell. Once the app is launched, we can change the placement of the app within the HoloLens Shell. Execution takes place once the app launch is completed. During the execution phase, the app goes through the app life cycle model of Resuming - Suspending - Activated state. The app life cycle is completed by removing the app from the HoloLens Shell.

The following diagram shows the application life cycle flow for a Holographic app running on HoloLens: