Mobile Computing - Unit 5

Cheatsheet Content

### Most Expected Questions This section outlines the most frequently asked questions from Anna University (R2021) exams for Unit 5: Mobile Platforms and Applications. Prioritize these for revision. #### 2-Mark Questions (Short Answers) - What is a Mobile OS? - Give four examples of mobile OS and their features. - What are the problems in Monolithic Kernel design? - What is a microkernel? - List the special constraints under which a mobile device needs to operate. - What is J2ME? What are its two configurations? - What is Android SDK? - What are Broadcast Receivers in Android? - What are the key components of Android architecture? - What is M-commerce? - List the applications of M-commerce (B2C and B2B). - Write the structure of mobile commerce (client side and server side). - Define POS. - Differentiate E-Commerce and M-Commerce. - List the pros and cons of M-commerce. - What is MIDP? - What are the major protocols involved in mobile payment systems? - What is HDML? - List the protocols used in WAP. - Differentiate native apps and web apps. #### 13-Mark Questions (Detailed Explanations) - Explain monolithic design versus microkernel design of an operating system. - Write short notes on special constraints and requirements of mobile OS. - Explain the components of Mobile Operating Systems. - Write in detail about a survey of commercial mobile operating systems / Explain various operating systems for mobile computing. - Write notes on J2ME configuration (CLDC, CDC, and profiles). - Explain in detail about Android SDK. - Briefly write how an application can be developed using the Android SDK. - Write short notes on Android software stack and Android application components. - What do you understand by M-Commerce? Explain advantages/disadvantages and applications of M-Commerce. - Explain the structure of mobile commerce and mobile payment system schemes with security issues. #### 16-Mark Questions (Comprehensive Essays) - Compare and contrast various mobile OS (Windows, Symbian, iOS, Android, Blackberry). - Explain Android SDK in detail with application development steps, software stack, and application components. - Explain M-Commerce in detail: structure, advantages, disadvantages, applications, and mobile payment schemes (bank account based, credit card based, micropayment based). - Explain J2ME architecture with configurations (CLDC, CDC) and profiles (MIDP, Foundation Profile, Personal Profile, etc.). ### Mobile OS Basics #### 1. What is a Mobile OS? (2-Marks) - **Definition:** A Mobile OS (Operating System) is the software platform that facilitates the efficient utilization of a mobile device's resources by performing multiple tasks. - **Functions:** It manages the processor, memory, files, and attached devices such as camera, speaker, keyboard, and screen. - **Purpose:** Enables applications to run by abstracting mobile system hardware details, allowing programmers to develop applications without deep knowledge of specific device specifications. #### 2. Examples of Mobile OS and Their Features (2-Marks) - **Windows Mobile:** Graphics/windows/event manager handles all input and output. - **Palm OS:** Single-tasking operating system. - **Symbian OS:** Real-time multitasking, pre-emptive, 32-bit operating system. - **iOS:** Contextual OS, Apple's mobile operating system for iPhone, iPad, and iPod Touch. - **Android OS:** Structured into four different layers. - **Blackberry OS:** High level of security. #### 3. Special Constraints and Requirements of Mobile OS (2-Marks & 13-Marks) Mobile OS operates under unique constraints compared to desktop OS: - **Limited Memory:** Less permanent and volatile storage. - **Limited Screen Size:** Restricts the display area and complexity of user interfaces. - **Miniature Keyboard:** Typing and command entry can be difficult. - **Limited Processing Power:** Processors are often ARM-based with restricted power, storage, and battery life. - **Limited Battery Power:** Requires efficient power management. - **Fluctuating Bandwidth:** Wireless medium offers variable and often limited network connectivity. - **Resource Management:** Must efficiently manage CPU, memory, and I/O for multiple applications. - **User Interface:** Must provide intuitive interfaces for touch-based interactions. - **Interfacing:** Provides interfaces for communication between processes, threads, and ISRs (Interrupt Service Routines). - **Middleware:** Provides middleware for system hardware abstraction. - **Task Management:** Offers management functions (creation, activation, deletion, suspension, delay) and scheduling mechanisms for tasks (semaphores, threads, priority allocation). #### Common Mistakes to Avoid: - Confusing mobile OS features with general OS features. - Not mentioning specific mobile constraints like battery life or screen size. ### Kernel Design: Monolithic vs. Microkernel #### 1. What are the problems in Monolithic Kernel design? (2-Marks) - **Massive Size:** Traditional OS like UNIX and Windows have monolithic kernels that are large and complex. - **Non-Modular:** All services (process management, memory management, I/O, file system, device drivers, networking) run in kernel space. - **Hard to Tailor:** Difficult to customize for specific needs. - **Hard to Maintain & Extend:** Changes in one part can affect others, making maintenance and adding new features challenging. - **Security Risks:** A bug in any service can crash the entire system. #### 2. What is a microkernel? (2-Marks) - **Definition:** A microkernel is a kernel design that minimizes the size of the kernel code. - **Functionality:** Only basic hardware-dependent functionalities and critical functions (like inter-process communication, I/O control, fundamental process management) are implemented in kernel mode. - **User Mode Services:** Other system services (e.g., file systems, device drivers, networking) run in user space as separate processes called "servers." - **Communication:** Services communicate via message passing (IPC). - **Benefits:** Easier to port, extend, and maintain OS code; enhanced stability and security. #### 3. Explain Monolithic vs. Microkernel Design (13-Marks) | Feature | Monolithic Kernel | Microkernel | | :------------------ | :------------------------------------------------------- | :------------------------------------------------------------- | | **Structure** | All OS services run in kernel space as a single process. | Basic services in kernel space; other services run as user-space servers. | | **Size** | Large and complex. | Small and compact. | | **Memory** | All services share the same address space. | Services run in separate address spaces. | | **Communication** | Direct function calls between services. | Message passing (IPC) between kernel and user-space servers. | | **Performance** | Generally faster due to direct calls. | Potentially slower due to IPC overhead. | | **Reliability/Stability** | A bug in one service can crash the entire system. | Failure of one service doesn't crash the entire system. | | **Extensibility** | Difficult to extend or modify. | Easier to extend; new services can be added without modifying the kernel. | | **Portability** | Difficult to port to new architectures. | Easier to port due to minimal kernel code. | | **Examples** | Unix, Linux | Mac OS, Windows NT | | **Advantages** | High performance, simpler design for basic OS. | High reliability, modularity, flexibility, easier debugging. | | **Disadvantages** | Less secure, less flexible, difficult to maintain. | Potential performance overhead, more complex communication. | #### One-line Revision Notes: - **Monolithic:** Big kernel, fast but fragile, all-in-one. - **Microkernel:** Small kernel, resilient but slower, modular services. ### Commercial Mobile Operating Systems #### 1. Survey of Commercial Mobile OS / Various Operating Systems (13-Marks & 16-Marks) This section details prominent commercial mobile operating systems, their features, and design philosophies. ##### a. Windows Mobile OS - **Features:** - **GWE (Graphics/Window/Event) Manager:** Handles all input and output. - **Virtual Memory Management:** Provides efficient memory utilization. - **Security:** Supports through a cryptographic library. - **Application Development:** Similar to Win32 environment, leveraging existing programmer knowledge. - **Multitasking:** Historically, didn't provide true multitasking (background apps hibernated); expected to support it in future versions. - **Key Point:** Designed to extend the Windows desktop experience to mobile devices. ##### b. Symbian OS - **Features:** - **Communication Protocols:** Supports TCP, UDP, PPP, DNS, FTP, WAP, Bluetooth, Infrared, USB. - **Pre-emptive Multitasking:** Efficiently manages multiple tasks. - **Memory Protection:** Isolates processes for stability. - **Microkernel-based:** Inherits benefits of microkernel architecture. - **Power Optimization:** CPU switches to low-power mode when inactive. - **Object-Oriented Design:** Applications and OS follow an object-oriented paradigm. - **Event-based Programming:** Utilizes "active objects" for event handling and CPU power saving. - **Development Environment:** Carbide (IDE toolkit for C++ development) based on Eclipse. - **Key Point:** Optimized for low-power, low-memory devices, strong in communication. ##### c. iOS - **Features:** - **Proprietary & Closed:** Owned and controlled by Apple, not licensed to third-party hardware. - **User Interaction:** Introduced innovative gestures like swipe, tap, pinch, reverse pinch. - **Sensors:** Utilizes internal accelerometers for features like shaking to undo, screen rotation. - **Market Presence:** Dominant due to iPhone's popularity. - **Key Point:** Focus on user experience, tightly integrated hardware/software, and innovative touch interface. ##### d. Android OS - **Features:** - **Linux Kernel-based:** Built on a modified Linux kernel. - **Open Source:** Highly customizable and widely adopted. - **Layered Architecture:** Structured into four main layers (Linux Kernel, Hardware Abstraction Layer, Android Runtime, Application Framework, Applications). - **Components:** Key components include Activities, Services, Broadcast Receivers, Content Providers. - **Development:** Uses Android SDK for Java/Kotlin application development. - **Key Point:** Open-source, highly flexible, vast ecosystem, and component-based application model. ##### e. BlackBerry OS - **Features:** - **Security:** Known for high-level security, especially for enterprise communications (encrypted email). - **Multitasking:** Supports true multitasking. - **Proprietary:** Historically tied to BlackBerry hardware. - **Disadvantages:** - **Closed Architecture:** Limited device choice, all from Research In Motion. - **Limited Applications:** Fewer apps compared to iOS/Android. - **Complex Development:** More challenging application development. - **Costly Applications:** Apps tend to be more expensive. - **Key Point:** Strong security and enterprise focus, but limited ecosystem. #### One-line Revision Notes: - **Windows Mobile:** Desktop extension, GWE. - **Symbian:** Microkernel, power-optimized, C++, event-driven. - **iOS:** Apple-only, gesture-driven, tight integration. - **Android:** Linux-based, open, layered, component model. - **BlackBerry:** Secure, enterprise, closed ecosystem. ### J2ME (Java 2 Micro Edition) #### 1. What is J2ME? What are its two configurations? (2-Marks) - **J2ME Definition:** J2ME is a Java platform designed for resource-constrained devices like mobile phones. It includes a miniature JVM called KVM (Kernel Virtual Machine) to run small Java programs. - **Configurations:** 1. **CLDC (Connected Limited Device Configuration):** For low-end, resource-constrained devices (e.g., pagers, feature phones, PDAs) with limited memory (16-32 bit) and bandwidth. 2. **CDC (Connected Device Configuration):** For higher-end devices (e.g., set-top boxes, smart phones, automotive telematics systems) with 32-bit processors and more memory (2GB). #### 2. What are the important capabilities of J2ME programs? (2-Marks) - Opening UDP connections between two devices. - Establishing HTTP connections with a server. - Making socket connections. - Bluetooth programming. - Barcode scanning. #### 3. Write notes on J2ME configuration (CLDC, CDC, and profiles). (13-Marks & 16-Marks) J2ME uses a modular architecture comprising Configurations, Profiles, and Optional Packages to tailor the Java environment to diverse device capabilities. ##### a. J2ME Architecture Overview - **Configurations:** Define the basic JVM and a minimal set of core Java classes for a category of devices with similar memory and processing power. - **Profiles:** Build on top of configurations, providing APIs for specific device families and their unique user interface and networking needs. - **Optional Packages:** Provide additional APIs for specialized functionalities (e.g., database access, web services). ##### b. Configurations 1. **CLDC (Connected Limited Device Configuration)** - **Target Devices:** Low-end, resource-constrained devices like pagers, mobile phones, PDAs. - **Memory:** Typically 16-32 bit microprocessors, small memory footprint. - **Connectivity:** Low bandwidth, wireless network connection. - **JVM:** Kernel Virtual Machine (KVM) - a highly optimized, small-footprint JVM. - **Core APIs:** A subset of Java Standard Edition APIs, optimized for limited resources. - **Key Point:** Provides the lowest common denominator for small and resource-constrained devices. 2. **CDC (Connected Device Configuration)** - **Target Devices:** Higher-end devices like digital set-top boxes, home appliances, navigation systems, smart phones. - **Memory:** Typically 32-bit processors, more memory (e.g., 2GB). - **Connectivity:** Often wired (e.g., DTV cable) or high-end wireless. - **JVM:** CVM (C Virtual Machine) - a more robust JVM compared to KVM. - **Core APIs:** A larger subset of Java Standard Edition APIs, supporting more complex applications. ##### c. Profiles Profiles layer on top of configurations to provide specific APIs for device families, addressing their unique UI and application requirements. 1. **MIDP (Mobile Information Device Profile)** - **Base:** Built on CLDC. - **Target Devices:** Mobile phones and basic PDAs. - **Purpose:** Provides APIs for UI, persistent storage, networking (HTTP), and application lifecycle management for mobile information devices. - **Key Point:** The most popular profile for developing applications on feature phones. 2. **Foundation Profile** - **Base:** Built on CDC. - **Target Devices:** Devices needing a robust Java platform but not necessarily a graphical UI (e.g., embedded systems, networked devices). - **Purpose:** Provides a more complete set of Java SE APIs than CLDC, but without UI classes. - **Key Point:** Suitable for non-GUI networked devices. 3. **Personal Profile** - **Base:** Built on Foundation Profile. - **Target Devices:** Devices requiring a graphical UI and network connectivity, such as advanced PDAs and smart communicators. - **Purpose:** Adds AWT (Abstract Window Toolkit) subset for GUI development. 4. **Other Profiles (e.g., Mobile Information Device Profile (MIDP), Personal Basis Profile, RMI Profile)** - These further specialize the J2ME environment for particular device types or functionalities. ##### d. J2ME Application Development - Developers write Java applications that target a specific configuration and profile. - The compiled bytecode is then deployed to compatible devices. #### One-line Revision Notes: - **J2ME:** Java for small devices, KVM. - **CLDC:** Low-end devices, limited resources. - **CDC:** High-end devices, more resources. - **MIDP:** CLDC + UI/HTTP for phones. - **Profiles:** Add specific APIs on top of configurations. ### Android SDK and Application Development #### 1. What is Android SDK? (2-Marks) - **Definition:** The Android SDK (Software Development Kit) is a set of development tools used to develop applications for the Android platform. - **Components:** It includes required libraries, a debugger, an emulator, relevant documentation (APIs), sample source code, and tutorials. - **Purpose:** Enables developers to create, test, and debug Android applications. #### 2. What are Broadcast Receivers in Android? (2-Marks) - **Purpose:** Broadcast Receivers respond to broadcast messages (Intents) from other applications or the system. - **Mechanism:** Applications can initiate broadcasts (e.g., "data downloaded") and Broadcast Receivers intercept these to perform appropriate actions. - **Implementation:** Implemented as a subclass of `BroadcastReceiver` and messages are `Intent` objects. - **Code Example:** ```java public class MyReceiver extends BroadcastReceiver { public void onReceive(Context context, Intent intent) { // Handle the broadcast message } } ``` #### 3. What are the key components of Android architecture? (2-Marks & 13-Marks) Android applications are built using a set of fundamental building blocks. These are the main components: | Component | Description | | :---------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Activity** | - Represents a single screen with a user interface. - Performs actions on the screen. - Example: an email application might have an activity for listing emails, another for composing, and another for reading. - One activity is marked as the entry point when the app launches. - Implemented as a subclass of `Activity`. - **Code Example:** `public class MainActivity extends Activity {}` | | **Service** | - A component that runs in the background to perform long-running operations. - Does not provide a user interface. - Example: playing music in the background, fetching data over the network without blocking UI. - Implemented as a subclass of `Service`. - **Code Example:** `public class MyService extends Service {}` | | **Broadcast Receiver** | - Handles communication between Android OS and applications. - Responds to system-wide broadcast announcements (Intents). - Example: receiving notifications for "data downloaded." - Implemented as a subclass of `BroadcastReceiver`. - **Code Example:** `public class MyReceiver extends BroadcastReceiver { public void onReceive(Context context, Intent intent) {} }` | | **Content Provider** | - Supplies data from one application to others on request. - Data can be stored in the file system, database, or web. - Handles data and database management issues. - Implemented as a subclass of `ContentProvider`. - **Code Example:** `public class MyContentProvider extends ContentProvider { // ... }` | | **Broadcast Receiver** | - Handles communication between Android OS and applications. - Responds to system-wide broadcast announcements (Intents). - Example: receiving notifications for "data downloaded." - Implemented as a subclass of `BroadcastReceiver`. - **Code Example:** `public class MyReceiver extends BroadcastReceiver { public void onReceive(Context context, Intent intent) {} }` | | **Content Provider** | - Supplies data from one application to others on request. - Data can be stored in the file system, database, or web. - Handles data and database management issues. - Implemented as a subclass of `ContentProvider`. - **Code Example:** `public class MyContentProvider extends ContentProvider { // ... }` | | Content 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