1. What are the main differences between native and hybrid app development?  

   • Native Apps: Developed specifically for one platform (iOS or Android) using platform-specific languages (Swift/Objective-C for iOS, Java/Kotlin for Android). They offer better performance and integration with device features.  

   • Hybrid Apps: Built using web technologies (HTML, CSS, JavaScript) and run inside a native container. They are cross-platform but may not perform as well as native apps.  

2. What is the MVC architecture?  

   • Model: Manages data and business logic.  

   • View: Displays data to the user and sends user commands to the controller.  

   • Controller: Handles user input and updates the model and view accordingly.  

3. What is RESTful API?  

   RESTful API is an architectural style for designing networked applications. It uses HTTP requests to perform CRUD operations (Create, Read, Update, Delete) on resources, which are identified by URLs. It typically returns data in JSON or XML format.  

4. What is dependency injection, and why is it important?  

   Dependency Injection (DI) is a design pattern in which an object's dependencies are provided by an external entity rather than the object itself. DI promotes loose coupling, making the code more modular, testable, and maintainable.  

5. Explain the concept of responsive design.  

   Responsive design is an approach to web and app development that ensures an application's UI adapts to different screen sizes and orientations, providing an optimal user experience across devices (mobile, tablet, desktop).  

6. What are push notifications?  

   Push notifications are messages sent from a server to a user's device, even when the app is not active. They are used to engage users with updates, reminders, and other relevant information.  

7. What is the difference between synchronous and asynchronous programming?  

   • Synchronous Programming: Tasks are executed one after the other, blocking further execution until the current task is complete.  

   • Asynchronous Programming: Tasks are executed independently, allowing the program to continue running while waiting for the task to complete.  

8. What is a singleton pattern?  

   The singleton pattern ensures that a class has only one instance and provides a global point of access to it. This is often used for managing shared resources, like database connections or configuration settings.  

9. What are the main differences between GET and POST HTTP methods?  

   • GET: Used to request data from a server. The parameters are included in the URL, making it suitable for read-only operations.  

   • POST: Used to send data to a server to create or update resources. The data is sent in the body of the request, making it more secure for sensitive information.  

10. What is a fragment in Android?  

    A fragment is a reusable component that represents a portion of the UI in an Android activity. Fragments allow for modular app design and dynamic UI changes within activities.  

11. What is the difference between a thread and a process?  

    • Process: An independent program with its own memory space. It can contain multiple threads.  

    • Thread: A smaller unit of execution within a process, sharing the same memory space as other threads in the process.  

12. What is the purpose of a ViewModel in Android?  

    A ViewModel is part of the Android Architecture Components, designed to store and manage UI-related data in a lifecycle-conscious way. It allows data to survive configuration changes like screen rotations.  

13. What is Cocoa Touch?  

    Cocoa Touch is the iOS UI framework for building apps, providing the necessary classes and libraries for developing iOS applications, including touch-based interactions, animation, and networking.  

14. Explain the concept of sandboxing in iOS.  

    Sandboxing is a security mechanism in iOS that restricts apps to their own designated area in the file system, preventing them from accessing data or resources of other apps or the system itself.  

15. What is Core Data in iOS?  

    Core Data is a framework provided by Apple for managing the model layer of an application. It handles the storage, retrieval, and manipulation of data using an object graph and persistence framework.  

16. What is the difference between synchronous and asynchronous tasks in Android?  

    • Synchronous Tasks: Executed sequentially, blocking the main thread until completion.  

    • Asynchronous Tasks: Executed in the background, allowing the main thread to remain responsive.  

17. What is Flutter, and how does it differ from React Native?  

    Flutter is an open-source UI software development kit (SDK) by Google for building natively compiled applications for mobile, web, and desktop from a single codebase using the Dart language. React Native, by Facebook, uses JavaScript and React to build cross-platform apps, relying on native components.  

18. What is the purpose of the Gradle build system in Android?  

    Gradle is a build automation tool used in Android development to compile code, manage dependencies, and package APKs. It provides flexibility and control over the build process.  

19. What is the difference between a service and an intent in Android?  

    • Service: A component that performs long-running operations in the background without a user interface.  

    • Intent: A messaging object used to request an action from another app component, like starting an activity, service, or broadcasting a message.  

20. What is ProGuard in Android?  

    ProGuard is a tool that shrinks, optimizes, and obfuscates Java bytecode. It reduces the size of the APK and makes it harder to reverse-engineer the app by obfuscating class, method, and variable names.  

21. Explain the lifecycle of an Android activity.  

    The Android activity lifecycle consists of several states:  

    • onCreate(): Called when the activity is first created.  

    • onStart(): Called when the activity becomes visible to the user.  

    • onResume(): Called when the activity starts interacting with the user.  

    • onPause(): Called when the activity loses focus but is still visible.  

    • onStop(): Called when the activity is no longer visible.  

    • onDestroy(): Called before the activity is destroyed.  

22. What is Auto Layout in iOS?  

    Auto Layout is a constraint-based layout system in iOS that allows developers to create adaptive and responsive UIs by defining relationships between UI elements. It ensures the app's UI looks good on different screen sizes and orientations.  

23. What are coroutines in Kotlin?  

    Coroutines are a feature in Kotlin that allows asynchronous programming without blocking threads. They simplify code by allowing it to be written sequentially while handling long-running tasks in the background.  

24. What is a ContentProvider in Android?  

    A ContentProvider manages access to a structured set of data, allowing apps to share data with other apps securely. It provides methods for querying, inserting, updating, and deleting data.  

25. What is the purpose of the Interface Builder in Xcode?  

    Interface Builder is a visual tool in Xcode for designing user interfaces. It allows developers to create and configure UI elements graphically, defining layouts, constraints, and relationships between UI components.  

26. What is an application context in Android?  

    Application context is a global context tied to the lifecycle of the application. It is used to access app-wide resources and services, like the file system or databases.  

27. What is the significance of the Main Thread in Android?  

    The Main Thread, also known as the UI Thread, is where all user interface operations and updates occur. It is crucial to keep this thread responsive to avoid making the app appear sluggish or unresponsive.  

28. What is the use of the Data Binding Library in Android?  

    The Data Binding Library allows developers to bind UI components directly to data sources in layouts, reducing boilerplate code and improving app performance by updating the UI automatically when the data changes.  

29. Explain the concept of asynchronous tasks in iOS.  

    Asynchronous tasks in iOS, often handled using Grand Central Dispatch (GCD) or Operation Queues, allow tasks to run in the background, keeping the main thread free to handle user interactions. This improves app responsiveness and user experience.  

30. What is the difference between the let and var keywords in Swift?  

    • let: Declares a constant, meaning the value cannot be changed after it’s set.  

    • var: Declares a variable, meaning the value can be changed after it’s set.