The Android user interface is based on the concept of direct manipulation whereby mono and multi-touch inputs such as swipes, touches, and pinches on the screen are used to manipulate objects visible on it. The response to user input was designed to be immediate and attempt to provide a smooth interface. Internal hardware sensors such as accelerometers, gyroscopes, and proximity sensors are used by some applications to respond to user actions, such as adjusting the screen from vertical to horizontal depending on how the device is oriented or allowing the user to drive a vehicle in a virtual race by turning the device, simulating the control of a steering wheel.
Android (unlike iOS) allows you to clear the cache both overall and individually for the specific app/service. There is also a command that allows you to free RAM from running but not essential apps/services. In addition to the specific cache, the command also allows you to delete the data stored by the single app: in practice, you get the app as if it were just installed. Finally, this menu is the one that can be used to terminate the app/service rather than uninstall, being able to also select the system services (advanced view).
The main screen, identified with an icon representing a house, is similar to the Windows desktop and is the one where you are as soon as the device has been started, or by pressing the Home button. This is generally occupied by both application icons and widgets, a sort of gadget with various functions; there are widgets that show various styles of watches, those that show the latest YouTube videos, others that display weather information, those related to email. The actual main screen (i.e. the initial screen) can be integrated by other pages including the user can scroll back and forth.
A classic component of the Android world is the Launcher (lit. “launcher”) or the system application that oversees and essentially manages the main screen and, secondly, the shortcuts (shortcut), the application drawer (app drawer), the bar bottom and the status bar, the notifications menu, and quick settings. In addition to the default, there are numerous third-party launchers that offer a wide range of customizations.
The shutdown menu is the area of the controls that appear when you press the on / off button (the commands are usually: turn off, restart, airplane / offline mode, emergency mode), sometimes followed at the bottom by the audio commands. Pressing another key or tapping on any other area the menu disappears.
Always present at the top of the screen is a status bar, which shows information about the device and its connectivity. Instead, in the lower part of the screen, there is usually the lower bar of standard applications: this remains fixed as the screens scroll. By dragging the status bar downwards, a notification screen appears in which applications can display notifications relating to important information or updates such as an e-mail or a text message, so as not to immediately interrupt the user. In the first versions of Android, these notifications could only be used to open the application in question, but the most recent updates have provided greater functionality, such as the possibility of calling a number directly from the notification of the missed call, without having to open the phone application Notifications are persistent until they are read or deleted by the user.
The platform uses the SQLite database, the dedicated SGL library for two-dimensional graphics (instead of the classic X server of the other Linux distributions), and supports the OpenGL ES 2.0 standard for three-dimensional graphics. Applications are run through the Dalvik virtual machine, a virtual machine adapted for use on mobile devices.
Android was designed primarily for smartphones and tablets, but the open and customizable character of the operating system allows it to be used on other electronic devices including laptops and netbooks, smartbooks, eBook readers, cameras, and smart TVs (Google TV). The “smart things” market has grown significantly in recent times to the point of stimulating people’s creativity. An example is a smartwatch equipped with a “light” Android operating system, headphones, car CD and DVD players, smart glasses (Google Glass), refrigerators, satellite navigation systems for vehicles, home automation systems, game consoles, mirrors, cameras, MP3 / MP4 players and treadmills.
The Android logo was designed with the Ascender Corporation’s Droid font family, green is the color of the robot that represents the Android operating system. The print color is PMS 376C and the RGB color in hexadecimal is # A4C639, as specified by the Android brand guidelines. The custom Android font is called Norad. It is used only in the text logo.
Applications (or apps) are the most generic form of indicating application software that can be installed on Android. They can be downloaded both from the official Google Play catalog and from other catalogs, such as the Amazon Appstore of Amazon.com, or F-Droid which contains only free-licensed software. Android applications can be installed directly from an APK file provided by the software distributor.
For IT security reasons, the applications are provided with a certification system that verifies the integrity of the package to be installed and the authorship with respect to a software distributor accredited by Google.
Android is equipped with a series of pre-installed applications ranging from the browser to the analog FM radio, from the calendar to the Gmail application, from the calculator to the Turn-by-Turn satellite navigator and also includes Google voice search with the possibility to choose the language in Italian.
In order to encourage the development of applications for the platform, the company Google organized in 2008 a prize competition linked to the development of applications for Android. The sweepstakes awarded a series of prizes and incentives to the applications, the choice of the winning applications were made internally by Google and the sum of the prizes was 10 million dollars. To comply with US legislation against terrorism or local bureaucratic impediments programmers residing in Cuba, Iran, Syria, North Korea, Sudan, Burma (Myanmar), Quebec, and Italy were excluded. Italy was excluded due to its legislation on prize winnings although his exclusion had been much discussed.
Since Android devices are generally battery-powered, Android is designed to manage processes to minimize energy consumption. When an application is not in use, the system restricts its use of resources so that although available for immediate use, it does not use significant amounts of battery or CPU resources. Android automatically manages applications stored in memory: when the memory is insufficient, the system begins, invisibly, to automatically close inactive processes, starting with those that have been inactive for long. In 2011 Lifehacker reported that third-party task killer applications do more harm than good.
Android provides a long list of advanced commands, useful for activating or deactivating or configuring or monitoring behaviors, functions, services, adjustments, information. This menu is deactivated by default but can be activated by quickly tapping 7 times on “Build number” in Settings \ Phone information \ Software information. Subsequently, it can be deactivated by using the on / off switch next to the new item which appears in settings (Developer Options).
For example, in the menu, there is the command to allow you to connect the device to a PC with a USB cable.
The main hardware platform of Android is ARM (the ARMv7 and ARMv8-A architectures), with x86 and x86-64 architectures officially supported also in the versions following Lollipop. The unofficial Android-x86 project provided support for x86 architectures before official support. ARMv5TE and MIPS32 / 64 architectures were also historically supported but were later removed. Android devices with Intel processors began to appear in 2012, including phones and tablets. While gaining support for 64-bit platforms, Android was initially created to run on 64-bit x86 architectures and then ARM64. From Android 5.0 “Lollipop” 64-bit variants of all platforms are supported in addition to 32-bit variants.
The minimum RAM requirements for devices with Android 7.1 range from 2GB for the best hardware, up to 1GB for mid-range devices, to the absolute minimum of 512MB for 32-bit smartphones with lower specifications. The recommendation for Android 4.4 must have at least 512 MB of RAM, while for “low RAM” devices 340MB is the minimum amount required that does not include the memory dedicated to various hardware components such as the baseband processor. Android 4.4 requires a 32-bit ARMv7, MIPS or x86 architecture processor (the latter two through unofficial ports), along with a graphics processing unit compatible with OpenGL ES 2.0 (GPU). Android supports OpenGL ES 1.1, 2.0, 3.0, 3.1 and from the latest version, 3.2 and from Android 7.0 Vulkan (and version 1.1 available for some devices). Some applications may explicitly require a specific version of OpenGL ES and adequate GPU hardware is required to run these applications.
Android devices incorporate many optional hardware components, including cameras or camcorders, GPS, orientation sensors, dedicated game controls, accelerometers, gyroscopes, barometers, magnetometers, proximity sensors, pressure sensors, thermometers, and touch screens. Some hardware components are not required but have become standard in some classes of devices, such as smartphones, and if additional requirements are present they apply. Some other hardware was initially required, but these requirements have been completely reduced or eliminated altogether. For example, since Android was initially developed as the phone’s operating system, hardware such as microphones were needed, while over time the phone’s function became optional. Android needed an autofocus camera, which was relaxed with a fixed focus camera if any since the camera was dropped as a requirement entirely when Android started using it on set-top boxes.
In addition to running on smartphones and tablets, several vendors run Android natively on normal PC hardware with a keyboard and mouse. In addition to their availability on commercially available hardware, similar versions of Android for PC are available for free from the Android-x86 project, including custom Android 4.4. Using the Android emulator which is part of the Android SDK or third-party emulators, Android can also work non-natively on x86 architectures. Some Chinese companies are building a PC and a mobile operating system, based on Android, to “compete directly with Microsoft Windows and Google Android”. The Chinese Academy of Engineering noted that “more than a dozen” companies were customizing Android following a Chinese ban on using Windows 8 on government PCs.