Operating system software (also operating system or OS) is
|“||a special collection of computer programs that has two primary purposes. First, operating systems provide the interface between application programs and the CPU and other hardware components. Second, operating systems load and run other programs.||”|
|“||the group of programs that monitor and control the operation of the computer system ￼￼while the application programs are running.||”|
|“||a program that manages the resources of the computer, allocating those resources to other programs as needed. It manages the computer's most basic functions, including the user's interaction with the device.||”|
|“||[t]he software 'master control application' that runs the computer. It is the first program loaded when the computer is turned on, and its main component, the kernel, resides in memory at all times. The operating system sets the standards for all application programs (such as the Web server) that run in the computer. The applications communicate with the operating system for most user interface and file management operations.||”|
Operating systems can be classified as follows:
- multi-user: Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
- multiprocessing: Supports running a program on more than one CPU.
- multitasking: Allows more than one program to run concurrently.
- multithreading: Allows different parts of a single program to run concurrently.
- real-time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.
Operating systems include some built-in security features like user names, passwords, and permissions, to perform specific tasks, such as running certain applications or accessing specific information such as a file or a database.
Most operating systems also include a graphical user interface that enables the user to perform most tasks by clicking on-screen icons. Some examples of operating systems are Microsoft Windows, Unix, Linux, OS/390, z/OS, and Mac OS.
How they work
An OS is loaded into a computer by a boot program and then manages all the other programs (i.e., applications, services, or application-enabling programs such as middleware) running on the computer. All computers, from small embedded processors to large servers supporting tens of thousands of users, require an OS. Most OSs have been designed and implemented to provide a wide range of features and services.
- Technology Assessment: Cybersecurity for Critical Infrastructure Protection, at 141.
- Information Technology: Tools and Techniques for Improving the Efficiency of Federal Automatic Data Processing Operation, at 19.
- Apple Inc. v. Corellium, LLC, 2020 WL 8642269, at *2 (S.D. Fla. 2020).
- NISTIR 7621 Rev. 1, at A-2.
- Battlefield operating system
- Card operating system
- Closed source operating system
- Cloud operating system
- Disk operating system
- Full-feature operating system
- Guest operating system
- Limited-feature operating system
- Host operating system
- Mobile operating system
- Network operating system
- Operating system fingerprinting
- Operating system virtualization
- Trusted operating system