Software designed to control the hardware of a specific data-processing system in order to allow users and application programs to make use of it.
Attributive form of operating system, noun.
The software that controls the basic operation of a computer or computer network.
The computer's master control program. When a computer is turned on, a small "boot program" loads the operating system. Although additional system modules may be loaded as needed, the main part, known as the "kernel" resides in memory (RAM) at all times.The operating system (OS) sets the standards for all application programs that run in the computer. Applications "talk to" the operating system for all user interface and file management operations. Also called an "executive" or "supervisor," an operating system performs the following functions.User InterfaceAll graphics based today, the user interface includes the windows, menus and method of interaction between the user and the computer. Prior to graphical user interfaces (GUIs), all operations were performed by typing in commands. However, command-line interfaces are not extinct. In fact, they are included in all major operating systems, and technical operations are commonly executed from the command line by programmers and administrators. Command line statements often get the job done more efficiently than with a GUI, and they are easily grouped in a file and executed all at once. See batch file, PowerShell and shell script.Operating systems may support optional interfaces. Although the overwhelming majority of people work with the default interface, different "shells" offer variations of functionality, and "skins" provide different appearances. See GUI, shell and skin.Job ManagementJob management controls the time and sequence that applications or utilities are run. Common in the server and mainframe environment, IBM's job control language (JCL) was developed decades ago to schedule the daily work. The execution of scripts throughout the day or at the end of a day, week or month is common in the server world.Task ManagementMultitasking, which is the ability to simultaneously execute multiple programs, is available in all operating systems today. Critical in the server and mainframe environment, applications can be prioritized to run faster or slower depending on their purpose. In the desktop world, multitasking is more often than not "task switching," which keeps applications open so users can bounce back and forth among them. See multitasking.Data ManagementData management keeps track of the data in storage (disk or SSD). The application program deals with data by file name and a particular location within the file. The operating system's file system knows where the data are physically stored (which sectors), and interaction between the application and operating system is through the programming interface (API). When an application needs to retrieve or save data, it makes a call to the file system, which is in charge of actually opening, reading, writing and closing files. See SSD, API and file system.Device ManagementDevice management controls peripheral devices by sending them commands in their proprietary machine language. The software routine that deals with each device is called a "driver," and the OS requires drivers for each of the peripherals attached to the computer. When a different type of peripheral is attached, that device's driver must be added to the operating system if not previously installed. See driver.SecurityOperating systems provide password protection to keep unauthorized users out of the system. Activity logs are maintained, which may provide time accounting for billing purposes. They generally provide backup and recovery routines for starting over in the event of a system failure.
HistoryIn the 1950s, programmers wrote their own input/output routines to read and write magnetic tape. When magnetic disks came on the scene several years later, it became essential to have a separate program to manage them as data were added and deleted. In addition, running more than one application at a time (timesharing and multitasking) required a control program to keep track of everything. Thus, the operating system was born. Today, most all computing devices use an operating system, the exception being a device with custom hardware (see ASIC). Common Operating SystemsThe primary computer operating systems in use are Windows Server, Windows XP, 7, 8 and 10, macOS, the many versions of Linux and Unix, IBM i (from the midrange AS/400) and z/OS (IBM mainframes). DOS is still used for some applications, and there are several more (see real-time system and embedded system).Mobile operating systems provide almost the same functions as the OS in a desktop computer or server. Smartphones and tablets use Apple's iOS, Google's Android, BlackBerry's QNX and Microsoft's Windows 10 Mobile.
Software designed to handle basic elements of computer operation, such as sending instructions to hardware devices like disk drives and computer screens, and allocating system resources such as memory to different software applications being run. Given uniformly designed operating systems that run on many different computers, developers of software do not need to concern themselves with these problems, and are provided with a standard platform for new programs.