An operating system (OS) is software that controls computer hardware and software components while also providing common functions to computer programs. Time-sharing operating systems plan tasks to make the most of the system’s resources, and they may also include accounting software to track the cost of processing time, storage, printing, and other resources.
Although the software is usually executed directly by the hardware and repeatedly makes system calls to an Operating system activity or is obstructed by it, the operating system works as an interface among programs and the computer hardware for hardware functions such as input and output and memory distribution. From cellular phones and gaming systems to web servers and supercomputers, operating systems are present on several devices that incorporate a computer.
Microsoft Windows is the most popular general use personal computer operating system, with a market share of roughly 76.45%. Apple Inc.’s macOS is in second position (17.72%), and various Linux distributions are in third place (1.73%).  By 2020, Android will have a 72 percent market share in the mobile sector (which includes smartphones and tablets).
According to third-quarter 2016 data, Android has a market share of 87.5 percent on smartphones, with a rate of increase of 10.3 percent each year, followed by Apple’s iOS at 12.1 percent, with a 5.2% year-over-year loss in market share, and other operating systems at 0.3%.
The server and supercomputing industries are dominated by Linux contributions. For many purposes, other specialized types of operating systems (special-purpose operating systems) exist, such as embedded and real-time systems. Security-oriented operating systems are also available. Low system requirements are found in many operating systems. Others might have more stringent system requirements.
Some operating system needs installation or may come pre-installed with new computers (OEM-installation), while others can be actually run from media such as a live CD, flash memory, or USB stick.