The drum set is the instrument central to the rhythm section. It acts as the motor that drives the group. A drum set can contain a multitude of percussion instruments, but in jazz, it usually consists of only a few parts. The lowest drum, or bass drum, is played with a pedal. The hi-hat, also played with a pedal, is a duo of small cymbals that crash together.
A style resource defines the format and look for a UI. A style can be applied to an individual View (from within a layout file) or to an entire Activity or application (from within the manifest file). For more information about creating and applying styles, please read Styles and Themes.
Google's Android and Apple's iOS are operating systems used primarily in mobile technology, such as smartphones and tablets. Android, which is Linux-based and partly open source, is more PC-like than iOS, in that its interface and basic features are generally more customizable from top to bottom. However, iOS' uniform design elements are sometimes seen as being more user-friendly.