iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that presently powers many of the company's mobile devices, including the iPhone, and iPod Touch; it also powered the iPad prior to the introduction of iPadOS in 2019. It is the second most popular mobile operating system globally after Android. Originally unveiled in 2007 for the iPhone, iOS has been extended to support other Apple devices such as the iPod Touch (September 2007) and the iPad (January 2010). As of March 2018, Apple's App Store contains more than 2.1 million iOS applications, 1 million of which are native for iPads. These mobile apps have collectively been downloaded more than 130 billion times. The iOS user interface is based upon direct manipulation, using multi-touch gestures. Interface control elements consist of sliders, switches, and buttons. Interaction with the OS includes gestures such as swipe, tap, pinch, and reverse pinch, all of which have specific definitions within the context of the iOS operating system and its multi-touch interface. Internal accelerometers are used by some applications to respond to shaking the device (one common result is the undo command) or rotating it in three dimensions (one common result is switching between portrait and landscape mode). Apple has been significantly praised for incorporating thorough accessibility functions into iOS, enabling users with vision and hearing disabilities to properly use its products. Major versions of iOS are released annually. On all recent iOS devices, iOS regularly checks on the availability of an update, and if one is available, will prompt the user to permit its automatic installation. The current version, iOS 13 was released to the public on 19 September 2019, introducing user interface tweaks and a dark mode, along with features such as a redesigned Reminders app, a swipe keyboard, and an enhanced Photos app. iOS 13 does not support devices with less than 2 GB of RAM, including the iPhone 5s, iPod Touch (6th generation), and the iPhone 6 and iPhone 6 Plus, which still make up over 10% of all iOS devices. iOS 13 is exclusively for the iPhone and iPod touch as the iPad variant is now called iPadOS.
Wallpaper is a material used in interior decoration to decorate the interior walls of domestic and public buildings. It is usually sold in rolls and is applied onto a wall using wallpaper paste. Wallpapers can come plain as "lining paper" (so that it can be painted or used to help cover uneven surfaces and minor wall defects thus giving a better surface), textured (such as Anaglypta), with a regular repeating pattern design, or, much less commonly today, with a single non-repeating large design carried over a set of sheets. The smallest rectangle that can be tiled to form the whole pattern is known as the pattern repeat. Wallpaper printing techniques include surface printing, gravure printing, silk screen-printing, rotary printing, and digital printing. Wallpaper is made in long rolls which are hung vertically on a wall. Patterned wallpapers are designed so that the pattern "repeats", and thus pieces cut from the same roll can be hung next to each other so as to continue the pattern without it being easy to see where the join between two pieces occurs. In the case of large complex patterns of images this is normally achieved by starting the second piece halfway into the length of the repeat, so that if the pattern going down the roll repeats after 24 inches, the next piece sideways is cut from the roll to begin 12 inches down the pattern from the first. The number of times the pattern repeats horizontally across a roll does not matter for this purpose. A single pattern can be issued in several different colorways.