Operating System - Unit 5 - Android Operating System

 

Introduction to Android Operating System, Android Development Framework, Android Application Architecture, Android Process Management and File System, Small Application Development using Android Development Framework.   Android Operating System Android is a mobile operating system based on a modified version of the Linux kernel and other open-source software, designed primarily for touchscreen mobile devices such as smartphones and tablets. Android is developed by a partnership of developers known as the Open Handset Alliance and commercially sponsored by Google. It was disclosed in November 2007, with the first commercial Android device, the HTC Dream, launched in September 2008. It is free and open-source software. Its source code is Android Open Source Project (AOSP), primarily licensed under the Apache License. However, most Android devices dispatch with additional proprietary software pre-installed, mainly Google Mobile Services (GMS), including core apps such as Google Chrome, the digital distribution platform Google Play and the associated Google Play Services development platform. About 70% of Android Smartphone runs Google's ecosystem, some with vendor-customized user interface and some with software suite, such as TouchWizand later One UI by Samsung, and HTC Sense. Competing Android ecosystems and forksinclude Fire OS (developed by Amazon) or LineageOS. However, the "Android" name and logo are trademarks of Google which impose standards to restrict "uncertified" devices outside their ecosystem to use android branding. Features of Android Operating System Below are the following unique features and characteristics of the android operating system, such as:   1. Near Field Communication (NFC) Most Android devices support NFC, which allows electronic devices to interact across short distances easily. The main goal here is to create a payment option that is simpler than carrying cash or credit cards, and while the market hasn't exploded as many experts had predicted, there may be an alternative in the works, in the form of Bluetooth Low Energy (BLE). 2. Infrared Transmission The Android operating system supports a built-in infrared transmitter that allows you to use your phone or tablet as a remote control. 3. Automation The Tasker app allows control of app permissions and also automates them. 4. Wireless App Downloads You can download apps on your PC by using the Android Market or third-party options like AppBrain. Then it automatically syncs them to your Droid, and no plugging is required. 5. Storage and Battery Swap Android phones also have unique hardware capabilities. Google's OS makes it possible to upgrade, replace, and remove your battery that no longer holds a charge. In addition, Android phones come with SD card slots for expandable storage. 6. Custom Home Screens While it's possible to hack certain phones to customize the home screen, Android comes with this capability from the get-go. Download a third-party launcher like Apex, Nova, and you can add gestures, new shortcuts, or even performance enhancements for older-model devices. 7. Widgets Apps are versatile, but sometimes you want information at a glance instead of having to open an app and wait for it to load. Android widgets let you display just about any feature you choose on the home screen, including weather apps, music widgets, or productivity tools that helpfully remind you of upcoming meetings or approaching deadlines.   8. Custom ROMs Because the Android operating system is open-source, developers can twist the current OS and build their versions, which users can download and install in place of the stock OS. Some are filled with features, while others change the look and feel of a device. Chances are, if there's a feature you want, someone has already built a custom ROM for it. Architecture of Android OS The android architecture contains a different number of components to support any android device needs. Android software contains an open-source Linux Kernel with many C/C++ libraries exposed through application framework services. Among all the components, Linux Kernel provides the main operating system functions to Smartphone and Dalvik Virtual Machine (DVM) to provide a platform for running an android application. An android operating system is a stack of software components roughly divided into five sections and four main layers, as shown in the below architecture diagram. Applications Application Framework Android Runtime Platform Libraries Linux Kernel   1. Applications An application is the top layer of the android architecture. The pre-installed applications like camera, gallery, home, contacts, etc., and third-party applications downloaded from the play store like games, chat applications, etc., will be installed on this layer. It runs within the Android run time with the help of the classes and services provided by the application framework. 2. Application framework Application Framework provides several important classes used to create an Android application. It provides a generic abstraction for hardware access and helps in managing the user interface with application resources. Generally, it provides the services with the help of which we can create a particular class and make that class helpful for the Applications creation. It includes different types of services, such as activity manager, notification manager, view system, package manager etc., which are helpful for the development of our application according to the prerequisite. The Application Framework layer provides many higher-level services to applications in the form of Java classes. Application developers are allowed to make use of these services in their applications. The Android framework includes the following key services: Activity Manager: Controls all aspects of the application lifecycle and activity stack. Content Providers: Allows applications to publish and share data with other applications. Resource Manager: Provides access to non-code embedded resources such as strings, colour settings and user interface layouts. Notifications Manager: Allows applications to display alerts and notifications to the user. View System: An extensible set of views used to create application user interfaces. 3. Application runtime Android Runtime environment contains components like core libraries and the Dalvik virtual machine (DVM). It provides the base for the application framework and powers our application with the help of the core libraries. Like Java Virtual Machine (JVM), Dalvik Virtual Machine (DVM) is a register-based virtual machine designed and optimized for Android to ensure that a device can run multiple instances efficiently. It depends on the layer Linux kernel for threading and low-level memory management. The core libraries enable us to implement android applications using the standard JAVA or Kotlin programming languages. 4. Platform libraries The Platform Libraries include various C/C++ core libraries and Java-based libraries such as Media, Graphics, Surface Manager, OpenGL, etc., to support Android development. app: Provides access to the application model and is the cornerstone of all Android applications. content: Facilitates content access, publishing and messaging between applications and application components. database: Used to access data published by content providers and includes SQLite database, management classes. OpenGL: A Java interface to the OpenGL ES 3D graphics rendering API. os: Provides applications with access to standard operating system services, including messages, system services and inter-process communication. text: Used to render and manipulate text on a device display. view: The fundamental building blocks of application user interfaces. widget: A rich collection of pre-built user interface components such as buttons, labels, list views, layout managers, radio buttons etc. WebKit: A set of classes intended to allow web-browsing capabilities to be built into applications. media: Media library provides support to play and record an audio and video format. surface manager: It is responsible for managing access to the display subsystem. SQLite: It provides database support, and FreeType provides font support. SSL: Secure Sockets Layer is a security technology to establish an encrypted link between a web server and a web browser. 5. Linux Kernel Linux Kernel is the heart of the android architecture. It manages all the available drivers such as display, camera, Bluetooth, audio, memory, etc., required during the runtime. The Linux Kernel will provide an abstraction layer between the device hardware and the other android architecture components. It is responsible for the management of memory, power, devices etc. The features of the Linux kernel are: Security: The Linux kernel handles the security between the application and the system. Memory Management: It efficiently handles memory management, thereby providing the freedom to develop our apps. Process Management: It manages the process well, allocates resources to processes whenever they need them. Network Stack: It effectively handles network communication. Driver Model: It ensures that the application works properly on the device and hardware manufacturers responsible for building their drivers into the Linux build.   Android Applications Android applications are usually developed in the Java language using the Android Software Development Kit. Once developed, Android applications can be packaged easily and sold out either through a store such as Google Play, SlideME, Opera Mobile Store, Mobango, F-droid or the Amazon Appstore. Android powers hundreds of millions of mobile devices in more than 190 countries around the world. It's the largest installed base of any mobile platform and growing fast. Every day more than 1 million new Android devices are activated worldwide. Android Emulator The Emulator is a new application in the Android operating system. The Emulator is a new prototype used to develop and test android applications without using any physical device. The android emulator has all of the hardware and software features like mobile devices except phone calls. It provides a variety of navigation and control keys. It also provides a screen to display your application. The emulators utilize the android virtual device configurations. Once your application is running on it, it can use services of the android platform to help other applications, access the network, play audio, video, store, and retrieve the data.   Advantages of Android Operating System We considered every one of the elements on which Android is better as thought about than different platforms. Below are some important advantages of Android OS, such as: Android Google Developer: The greatest favourable position of Android is Google. Google claims an android operating system. Google is a standout amongst the most trusted and rumoured item on the web. The name Google gives trust to the clients to purchase Android gadgets. Android Users: Android is the most utilized versatile operating system. More than a billion individuals clients utilize it. Android is likewise the quickest developing operating system in the world. Various clients increment the number of applications and programming under the name of Android. Android Multitasking: The vast majority of us admire this component of Android. Clients can do heaps of undertakings on the double. Clients can open a few applications on the double and oversee them very. Android has incredible UI, which makes it simple for clients to do multitasking. Google Play Store App: The best part of Android is the accessibility of many applications. Google Play store is accounted for as the world's largest mobile store. It has practically everything from motion pictures to amusements and significantly more. These things can be effortlessly downloaded and gotten to through an Android phone. Android Notification and Easy Access: Without much of a stretch, one can access their notice of any SMS, messages, or approaches their home screen or the notice board of the android phone. The client can view all the notifications on the top bar. Its UI makes it simple for the client to view more than 5 Android notices immediately. Android Widget: Android operating system has a lot of widgets. This gadget improves the client encounter much and helps in doing multitasking. You can include any gadget relying on the component you need on your home screen. You can see warnings, messages, and a great deal more use without opening applications. Disadvantages of Android Operating System We know that the Android operating system has a considerable measure of interest for users nowadays. But at the same time, it most likely has a few weaknesses. Below are the following disadvantages of the android operating system, such as: Android Advertisement pop-ups: Applications are openly accessible in the Google play store. Yet, these applications begin demonstrating tons of advertisements on the notification bar and over the application. This promotion is extremely difficult and makes a massive issue in dealing with your Android phone. Android require Gmail ID: You can't get to an Android gadget without your email ID or password. Google ID is exceptionally valuable in opening Android phone bolts as well. Android Battery Drain: Android handset is considered a standout amongst the most battery devouring operating systems. In the android operating system, many processes are running out of sight, which brings about the draining of the battery. It is difficult to stop these applications as the lion's share of them is system applications. Android Malware/Virus/Security: Android gadget is not viewed as protected when contrasted with different applications. Hackers continue attempting to take your data. It is anything but difficult to target any Android phone, and each day millions of attempts are done on Android phones.             Process Management Overview Process Control Block(PCB) and Process Management Process state Process number Program counter Registers Memory limits List of Open files ... RunningReadyNew Exit Blocked At base level android PCB is the same and PCB is managed by standard process management   Process Management Application lifecycle 2 Process Management Priority Hierarchy 1  ❏ Linux reclaim memory by removing process with lowest priority ❏ There are five levels in priority hierarchy ❏ Android ranks a process the highest level it can Android ranks a process at the highest level it can, based upon the importance of currently active components. For example, if a process hosts a service and a visible activity, the process is ranked as a visible process, not a service process.   Process Management Priority Hierarchy ❏ Foreground process: A process that is required for what the user is currently doing ❏ Visible process: A process that doesn't have any foreground components, but still can affect what the user sees on screen ❏ Service process: A process that is running a service. Started with startService() method ❏ Background process: A process holding an activity that's not currently visible to the user (the activity's onStop() method has been called) ❏ Empty process: A process that doesn't hold any active application components. Only alive for caching purposes   Important Terms to study   1.       The Mobile operating system 2.       The Android  device. 3.       The application framework 4.       NFC type of communication 5.       Android 6.       Android Architecture 7.       Emulator Application 8.       Processor management hierarchies 9.       Features of Android Operating System 10.   Types of Android applications. 11.   Process control block of android system