All about android operating systems

Операционная система Android

Feb 4 · 6 min read

Android — это операционная система с открытым исходным кодом, созданная для мобильных устройств на основе модифицированного ядра Linux. Эта ОС разработана консорциумом Open Handset Alliance, состоящим из крупных технологических компаний при организующей роли Google. Исходный код ОС представлен как часть проекта Android Open Source Project (AOSP) с лицензией Apache. Выпущенный на рынок в 2007 году Android вскоре стал самой продаваемой операционной системой в истории, благодаря своей открытой модели разработки и удобному интерфейсу. Последняя версия Android 11 вышла в 2020 году.

История развития

Проект Android появи л ся в 2003 году с целью разработки интеллектуальных мобильных устройств. Начинался он с разработки ОС для цифровых фотокамер, но вскоре акцент сместился на мобильные телефоны из-за их большой распространенности на рынке. В 2005 году проект приобрел Google и в качестве основы для этой ОС было выбрано ядро Linux за счет его гибкости и возможности обновления.

С целью разработки платформы с открытым исходным кодом для мобильных устройств в 2007 году Google сформировала Open Handset Alliance с несколькими производителями оборудования и операторами беспроводной связи. В то время каждый производитель выпускал мобильные телефоны на базе собственной платформы, с ограниченными возможностями для сторонних приложений. Альянс заявил, что открытая платформа обеспечит тесное сотрудничество между производителями и разработчиками, чтобы ускорить производство недорогих инновационных продуктов и приложений.

Платформа Android была представлена в 2007 году и вышла на рынок на следующий год. Поначалу ей мешал ограниченный набор функций и небольшая база пользователей по сравнению с конкурентами Symbian и Windows. Однако возможность обновления стала самым большим преимуществом этой ОС, поскольку каждое обновление давало новые функции и улучшенную производительность. Из-за «сладости, которую они приносят в нашу жизнь», первые версии были названы в честь десертов, в алфавитном порядке, например Cupcake, Jellybean и KitKat. Однако вскоре у Google закончились десерты, и с 2019 года новые версии ОС получают номера, начинающиеся с Android 10. Лицензия с открытым исходным кодом также помогла увеличить популярность этой ОС среди производителей мобильных устройств, поскольку они могут теперь модифицировать ОС под свои требования, не влияя при этом на разработку приложений.

Но самая главная особенность в том, что Android — это больше, чем просто операционная система. Он во многом уравнял мобильные устройства с персональными компьютерами, позволив разработчикам писать приложения независимо от аппаратной платформы устройства. Это привело к созданию глобальной платформы для приложений и укрепило позиции Android, как передовой мобильной платформы, и в 2011 году он стал самой продаваемой операционной системой для смартфонов и для планшетов в 2013 году. Сегодня на Android работает множество электронных устройств, включая смарт-камеры, часы, медиаплееры и многое другое.

Архитектура

Первоначально Android разрабатывался для архитектуры ARM, а затем был расширен для поддержки архитектур x86 и x86–64. Однако в целом Android не заботится об аппаратном обеспечении устройства из-за разнообразия и множества типов среди компонентов в мобильных устройствах.

Основой ОС Android является модифицированная версия ядра Linux LTS, которая непосредственно взаимодействует с оборудованием. Драйверы, необходимые для работы устройства, реализуются производителями оборудования и добавляются в ядро. Это позволяет производителям оборудования разрабатывать драйверы для хорошо известного ядра, а разработчикам ОС игнорировать разнообразие оборудования. Android 11 поддерживает версии ядра 4.14, 4.19 и 5.4.

Особенности оборудования дополнительно маскируются также реализуемыми производителями уровнями аппаратной абстракции, которые предоставляют стандартные интерфейсы для высокоуровневых структур, чтобы обеспечить доступ к аппаратному обеспечению устройства, не заботясь при этом о реализации драйверов.

Android Runtime (ART) — это виртуальная машина, которая выполняет код приложения, содержащийся в файлах Dalvik Executable (DEX). Она управляет компиляцией кода, отладкой и очисткой памяти. Каждое приложение работает со своим собственным экземпляром ART, то есть в своей собственной виртуальной машине, чтобы обеспечить изоляцию кода. ART заменил Dalvik в качестве виртуальной машины Java для Android в 2013 году, поскольку его компиляция Ahead-of-Time обеспечила лучшую производительность по сравнению с компиляцией Just-in-Time у последней.

Собственные библиотеки C/C ++ являются важной частью операционной системы, поскольку большинство основных компонентов Android написаны на собственном коде. Инфраструктура Java API — это шлюз в ОС для всех пользовательских приложений. Он предоставляет множество сервисов для приложений в виде вызовов Java API, включая менеджеры действий, ресурсов и уведомлений, поставщиков контента и систему просмотра. Именно поэтому приложения для Android в основном разрабатываются на Java, хотя собственные библиотеки обеспечивают некоторую поддержку C/C++. Совсем недавно также поддерживался и Kotlin, он даже предпочитался Google для разработки приложений Android. Код компилируется Android Software Development Kit (SDK) и архивируется в виде пакета Android (APK).

Android против Linux

Хотя некоторые считают Android дистрибутивом Linux, он имеет мало общего с обычной ОС Linux.

В традиционном стеке Linux ядро выполняет большую часть системных функций, включая управление памятью и файлами, аппаратное взаимодействие и планирование процессов. Системные функции предоставляются приложениям через библиотеки и вызовы API на языке Си. Именно поэтому GNU C является более важной библиотекой в Linux. Пользователи взаимодействуют с системой через оболочки, которые транслируют пользовательские команды в системные вызовы.

С другой стороны, Android можно рассматривать как пользовательское приложение, работающее в Linux. ОС использует ядро для взаимодействия с оборудованием и управления системой, а затем предлагает свои функции другим приложениям через интерфейс API. Этот интерфейс написан полностью на Java, и даже функции библиотек C/C ++ предложены в оболочках Java. В Android нет оболочки, хотя некоторые утилиты командной строки поддерживаются через приложение Toybox.

Кроме того, Android оптимизирован для мобильных устройств, которые обычно обладают малой вычислительной мощностью, имеют небольшой объем памяти и работают от батарей. По умолчанию, в качестве библиотеки C, вместо GNU, он использует Bionic из-за пониженных требований к памяти и процессору. При нехватке памяти, Android может уничтожить наименее используемые процессы и сбросить блоки разделяемой памяти. Кроме того, здесь реализуется уникальная система управления питанием, в которой устройство остается в спящем режиме, потребляя минимальную мощность до тех пор, пока процесс не запросит ресурс.

Ядро Android

Перед установкой на устройство само ядро Linux подвергается модификации несколькими участниками проекта. Во-первых, разработчики Android оптимизируют ядро LTS для мобильных устройств, вносят коррективы в функции Android и оставляют код как общее ядро AOSP. Разработчики AOSP реализуют большинство изменений в виде драйверов устройств, чтобы гарантировать внесение минимальных изменений в основной код ядра. Это позволяет с минимальными изменениями объединять обновления базового ядра в ACK. Поставщики оборудования добавляют драйверы и уровни абстракции для создания ядра поставщика. Затем, производители устройств обновляют ядро в соответствии со своими требованиями, реализуя новые драйверы или даже улучшая систему. Это ядро, в конечном счете, устанавливается на выпускаемые производителем устройства.

Разработка приложения

Основной принцип разработки в Android заключается в том, чтобы абстрагироваться от вариативности оборудования и предоставить унифицированный интерфейс для приложений. Это достигается запуском всех приложений на виртуальных машинах Java, подобных Dalvik или ART. Еще более способствует этой абстракции и упрощает разработку приложений комплект, состоящий из инфраструктуры Java API и SDK Android. Интерфейс API выполняет всю сложную работу, обеспечивая приложениям доступ к системным ресурсам лишь через вызов функции, в то время как SDK предоставляет визуальные инструменты для создания макетов приложений и управления вводом данных пользователя.

Android предоставляет приложениям большую часть своих функций через службы (services). Служба — это приложение, которое выполняет длительные операции в фоновом режиме. Она не предоставляет пользовательского интерфейса и доступна только через платформу API. Службы также могут выполнять операции в приоритетном порядке и сообщениями уведомлять пользователя. Служба также может быть привязана к приложению и обеспечивать интерфейс клиент-сервер.

Стек Android также включает вторую операционную систему Trusty. Она работает параллельно с основной операционной системой и обеспечивает доверенную среду для изолированного выполнения. В основном она используется для мобильных платежей, безопасного банковского обслуживания, обработки паролей и других процессов, требующих безопасности и конфиденциальности.

Заключение

При первых анонсах Open Handset Alliance их планы по взаимодействию при разработке открытой и многоцелевой платформы представлялись не более чем громким заявлением. Однако через десять лет платформа Android произвела революцию, и не только в мобильной индустрии. Фактически, она породила совершенно новые отрасли промышленности и коренным образом изменила наш образ жизни, работы и общения.

Источник

Documentation of Operating Systems and Developers

Android operating system

Android OS

The android platform was founded by Google and offers on the base the Linux kernel 2.6 a uniform interface for mobile equipment and programmes. Through this it is easily to port and is programmed in Java. After the conversion into the own binary program format Dalvik (.dex) it is not compatible to Java any more. Advantage is the faster execution and the lower memory footprint of programmes than in pure Java. Every Dalvik application is executed in a Dalvik VM of its own. Applications can access all equipment functions. This makes it possible for the programmer to make innovative programmes which offers the user high value by the combination of all sorts of data sources with the equipment functions.

The Eclipse IDE with an official plugin is used for the development. The operating system Android for Smartphones is supported by the Open Handset Alliance. Including more than 30 communication provider, equipment and semiconductor manufacturers as well as software companies. Because Android is an open platform in the meaning of the software and product development the source code shall be available completely at a later time and is in opposite with the market leading closed operating systems Symbian, Palm OS and Windows Mobile.

Android include C/C++ function libraries used by different parts of the operating system.

• Surface manager for 2D and 3D even overlay display
• System C library, specialized for Linux-based devices (BSD implementation)
• SGL, 2D graphic system
• 3D libraries, based on OpenGL ES 1.0 APIs with hardware or software accelerated 3D display
• Media libraries for playback and record of audio, graphic and video formats (MPEG4, H.264, MP3, AAC, AMR, JPG, PNG)
• LibWebCore, Android internet browser
• FreeType, for representing of bitmap and vector fonds
• SQLite, an efficient and slim relational database for all applications

The Android SDK is available for Linux, MacOS and Windows. It contains an emulator with the surface of Android to try applications. After unpacking the SDK the emulator can be found in the subdirectory » oolsemulator.exe» that shows a HTC Smartphone with keyboard.
Standard programs for e-mail, SMS, contacts, calendar, road maps, internet browser and others are preinstalled.

The first Google Android Developer Challenge (ADC) started in April 2008 for engaged programmers to realize and present ideas. Approximately 1,800 programmes were submitted and 20 honoured with a price money under the best 50. Part of the best applications are for example cab4me by combination of Google Maps, GPS signal and a database to send a taxi in the simplest mode by click to the current position on the map. Or GoCart which reads the bar code of goods with the mobile telephone camera and looks over onlineshops and registered shops in the circumference for the best price.

Google creates a sales platform for Smarthone applications with Android Market. At first the market place is provided free of charge. The first Android mobile telephone cames from the taiwanese manufacturer HTC with the T-Mobile G1 smartphone starting at October 22nd, 2008 in the USA and at the beginning of 2009 in Germany. The Android Market was renamed in Google Play on 6th March 2012.

The market research group Gartner, Inc. released a press news about the worldwide market share of smartphone ventors and operating systems on 19th August 2016. In the 2nd quarter 2016, 296.9 million Android units have been sold, this represents a market share of 86.2%. The Android operating system increased his share, in 2nd quarter 2015 the market share was 82.2% with 271.6 million units sold.

Источник

What is Android? Here’s everything you need to know

By now, most people know there are two prominent mobile operating systems: Google’s Android and Apple’s iOS. There used to be a lot more, but now pretty much every major mobile device runs one or the other. Being that this is a site with “Android” in its name, we might have visitors who wonder: “What is Android?” That’s actually a huge question, and we aim to answer it as thoroughly as possible here!

Even if you’re a smartphone pro, there could be a lot to learn about Android in the sections below. But if you’re new to the world of smartphones — or just the world of Android — this is the perfect place to get up-to-speed on the world’s most popular operating system.

What is Android? Here are the basics

Android is a mobile operating system that has been around for nearly 15 years. You’ll primarily find it as the base operating system of phones and tablets around the world. Additionally, there are other operating systems that natively support Android applications, including Chrome OS and Windows 11.

Search giant Google owns Android. However, the system is open source, which makes it freely accessible to anyone, even for commercial use. This makes Android very different from Apple’s iOS, macOS, and Microsoft’s Windows, which are all closed-source platforms.

Android is by far the world’s most popular operating system. Estimates suggest it runs on 2.5 billion active devices across the globe, with over three billion users — or roughly 39% of the entire global population. This dwarfs Apple’s iOS by a significant margin and even tops Microsoft’s Windows, which is the second-most-popular operating system globally.

There are over three million applications that work on Android. Most of these apps can be found on the official Google Play Store, but you can also sideload apps from the web. This variety makes Android phones very powerful and customizable — but also susceptible to viruses and other types of malware.

If you don’t know what some of these terms mean, don’t worry: we’re going to explain everything in more detail!

What is an operating system?

If you ask “What is Android?” you’re likely to hear back, “It’s an operating system.” That answer is only useful if you know what an operating system is!

In brief, an operating system is computer software that works to integrate hardware and software resources. It allows for different types of hardware to work together while simultaneously providing a platform for various bits of software to work with that hardware and, consequently, other pieces of software.

If that’s still confusing, think of the analogy of a stage play. To put on a play, you’ll need a stage, lights, microphones, and other pieces of hardware. You’ll also need actors, stage crew, ushers, and other workers, which would be analogous to software. In this analogy, the director of the play would be similar to an operating system, as they would act as a conduit that instructs everything on how to work together. Without the director, you’d just have a ton of unused hardware with a bunch of people running around with no idea what to do.

In the case of smartphones, Android acts as the “director” for the unique hardware in your phone and the apps you’ve chosen to install.

Where you’ll find Android — from phones to smartwatches

When most people think of Android, they think of phones. While it’s true that most Android devices are smartphones, there are plenty of other devices out there with Android on board.

Tablets are the most obvious secondary Android device. After all, they are just big phones, in many respects.

Android also appears on smartwatches. If you own a watch that runs on Wear OS, that is an Android-based operating system. What is an Android-based operating system? That’s when someone takes Android and tweaks it to make it something different but still based on the same core code.

There is also a TV platform, appropriately called Android TV. We also can’t forget about Android Automotive, which is Android-based software that powers vehicles. However, don’t confuse this with Android Auto, which is a way for smartphones to integrate with dash systems in cars.

Finally, there are other operating systems out there that are not based on Android but do support running Android apps. Recent versions of Chrome OS allow for this. That means pretty much all Chromebooks on the market also support Android apps. Starting in late 2021, Windows 11 will also support Android apps.

The early beginnings of Android

Believe it or not, Android started out as software for cameras. Andy Rubin and his team developed Android starting in 2003 by using core code from Linux, another open-source operating system. The idea was to make a universal operating system that all camera companies could use.

However, during the later development of Android, Rubin realized that smartphones were the future. He decided to revamp Android as a smartphone operating system instead. The idea didn’t attract much investment since Windows Phone, Symbian, and other phone operating systems were already dominating the market. Rubin and his team almost stopped development when they ran out of money.

In the end, a generous monetary gift from a friend kept the team going and Google swept in and bought Android for about $50 million in 2005. The Android team worked under Google to develop an operating system that worked well on mobile phones with physical buttons and full QWERTY keyboards.

However, the arrival of the iPhone in 2007 forced the team to go back to the drawing board. They revamped Android again to also work with touchscreens. This resulted in the HTC Dream, also known as the T-Mobile G1, the very first commercial Android phone. It had a touch screen and a QWERTY keyboard, as seen above.

Since then, there have been thousands of Android phones and it is now the most popular operating system in the world.

Android is open source, but what does that mean?

When something is open source it means the copyright owner allows its use for any purpose, without any need for financial remuneration. As mentioned earlier, the core code of Android is based on open-source software called Linux. This means that Android, by definition, must also be open source.

To better understand this, let’s look at the opposite: closed-source software. Apple’s iOS is closed source, which means that no one can use it unless the copyright holder — in this case Apple — gives permission. If you were to obtain the source code of iOS and release it on any device, Apple could sue you for infringement on its ownership.

With open-source software, this limitation is gone. Instead, the person or company using the software simply needs to abide by a set of rules related to the licensing of that software. Our own Gary Sims explains these rules in the video above. In brief, this means that their “new” software must also be open source and they must make the code easily available to anyone who would like to use it.

The open-source nature of Android is one of the main reasons it is the most popular operating system in the world. Since anyone can use it for free, it’s incredibly easy for companies of all sizes to create terrific products without needing to invest in creating their own operating system. This is why you find Android in all manners of electronics from all sorts of different brands.

You might be wondering why Google is OK with giving away this product for free. The explanation is actually pretty simple, some aspects of Android you use on your phone are not open source. As you’d imagine, these are some of the most vital apps and services made for Android.

What is Android’s Google Play Service?

The core of Android is open source, which we call “stock” Android. This software lands as part of the Android Open Source Project (AOSP). This is Android in its purest, most basic form.

However, the Android you get with almost all smartphones has tons of other software incorporated that is not open source. Most of this software falls under a system called Google Play Services. This brings Google-branded products to Android, including the Google Play Store, Gmail, YouTube, etc.

In other words, you can use AOSP software all you like for free, but you can’t use Google all you like. Just like with Apple’s tight control of iOS, Google tightly controls Google Play Services. To use it, you need a license and to agree to let Google earn money from your products.

Even though most of the world closely associates Google and Android, there are plenty of Android-based devices out there without Google Play Services. For example, Google does not allow most of its products in China. If you go there, you can easily find Android phones without Google. There will be app stores, apps, and all sorts of familiar features, but not from Google. A more US-centric example would be Amazon’s Fire tablets, which utilize a custom version of Android called Fire OS that substitutes Google apps for Amazon’s own in-house options.

Throughout most of the world, though, Google is inseparable from Android. This is by design. Android’s dependence on Google earns the company billions.

Who maintains Android?

The answer to this question has a few facets. In brief, Google employees maintain the core Android experience. They are responsible for adding new features, updating old ones, and making sure Android follows open-source principles.

However, there’s more to it than that. Most manufacturers also “skin” Android, which means they create their own software that lives on top of Android. This is why the Android you find on a Samsung phone and the Android you find on a OnePlus phone function similarly but look very different. Each manufacturer maintains its own Android skin.

There’s also the question of distributing Android. Obviously, your phone comes with a version of Android when you first take it out of the box. But how does it get updates? Depending on how you bought the phone, an update could need to pass through multiple rungs. First, it needs to come from Google. Then, it needs to get tweaked by your phone’s manufacturer to make sure the skin still works well. Then, it may need to go through your carrier, because it also usually customizes phones it sells.

This long chain of events is one of the big reasons why Android phones don’t see updates as often or for as long as iOS devices. For iPhones, Apple controls everything. There are no skins and carriers have little ability to interfere with how iOS looks and works. In essence, Apple can push an update to every iPhone around the world quickly and easily with little influence from carriers or other companies. Android phones don’t have this luxury.

Android versions: A brief history

As of today, there have been 18 versions of Android, with 11 major releases. The most recent stable version of the operating system is Android 11. We expect Android 12 to land later in 2021, at the end of August or the beginning of September, which will make it the 19th version and 12th major release.

Originally, Google named Android after “sweet treats.” Each treat name happened in alphabetical order, starting with the letter “C” in 2009. However, Google abandoned this trend in 2019 with the launch of Android 10.

Here are all the major Android releases:

• 2009 — Cupcake (v. 1.5)
• 2009 — Donut (v. 1.6)
• 2009 — Eclair (vs. 2.0, 2.0.1, and 2.1)
• 2010 — Froyo (vs. 2.2 through 2.2.3)
• 2010 — Gingerbread (vs. 2.3 through 2.3.7)
• 2011 — Honeycomb (vs. 3.0 through 3.2.6)
• 2011 — Ice Cream Sandwich (vs. 4.0 through 4.0.4)
• 2012 — Jelly Bean (vs. 4.1 through 4.3.1)

• 2013 — KitKat (vs. 4.4 through 4.4W.2)
• 2014 — Lollipop (vs. 5.0 through 5.1.1)
• 2015 — Marshmallow (vs. 6.0 through 6.0.1)
• 2016 — Nougat (vs. 7.0 through 7.1.2)
• 2017 — Oreo (vs. 8.0 and 8.1)
• 2018 — Pie (v. 9.0)
• 2019 — Android 10
• 2020 — Android 11

Android 11 introduced several new features related to messaging, privacy, security, and accessibility. However, it looked mostly the same as Android 10 and Android 9 Pie before it.

With Android 12, we expect Google to revamp the way the operating system looks and feels. There will also be even more features and controls related to privacy and security.

If you are curious which version of Android you have on your device, head to Settings > About > Software Information.

Android apps: How you can get them

Assuming you have a device with Google Play Services on board, the easiest and safest way to get Android apps is to use the Google Play Store. This comes pre-installed on all Google-supported phones, tablets, and other devices. Just open the app and search for whatever game, program, media, or other product you’re looking for. Many of them are free, but some will require payment.

If you don’t have a device with Google Play Services, you likely have access to a different app store. The most common example of this is Amazon devices, which come with the Amazon App Store pre-installed. Another example is modern Huawei devices, which will have App Gallery. Consult your device’s manufacturer if you are unsure as to which app store you should be using.

Regardless of your device’s particular app store, you can also manually install Android apps by downloading them from the open web. This is called “sideloading.” Generally, this practice is safe. However, there is an inherent security risk to sideloading apps as they do not need to meet the safety requirements enacted by app stores. As such, you should only sideload apps from trustworthy sources.

If you are looking for some suggestions of apps you should install, we have plenty of articles to help with that:

Android vs iOS: The mobile OS battle

We’ve already touched a few times on what makes Android different from Apple’s iOS. However, we want to point out that the two operating systems have become much more similar than different over the years.

In the early days of the smartphone industry, Android and iOS were wildly different. Each OS offered features the other didn’t. They also didn’t look at all similar. This dichotomy created an “Android vs iOS” culture that still pervades today.

Really, though, there are only a handful of things Android can do that iOS can’t (and vice versa). Google and Apple have been cribbing from each other so much over the years that the two operating systems are closer than ever.

The only distinct difference between the two is how much control Apple has over iOS — and how Google doesn’t have that same level of control over Android. It is impossible to sideload apps on an out-of-the-box iPhone, for example, and there’s only one app store (the Apple App Store). Apple also tightly controls the kinds of apps developers can make for iPhones.

By contrast, we’ve already discussed how easy it is for you to install Android apps from other stores or even from the open web. Additionally, Google allows you to choose which apps you use for pretty much every smartphone function, from your browser to your messaging apps to your keyboard.

The advantage to Apple’s model is that iOS is more uniform, safer, and allows devices to see updates for long periods of time. The downside, of course, is that the user doesn’t have as much say as to what they can do with their device.

If you are moving from an iPhone to Android, we also have a guide to help with that transition, as you can see here.

If you came to this article asking yourself, “What is Android?”, we hope you’ve found your answer! Be sure to bookmark this page, as we will update it with new information regarding Android versions as they launch.

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