Operating system
An operating system is a special computer program that manages the relationship between application software, the wide variety of hardware that makes up a computer system, and the user of the system.
The lowest level of any operating system is its kernel, the first layer of software loaded into computer memory when a system boots, or starts up. The kernel then provides access to various common core services to all other system and application programs. These services include, but are not limited to: disk access, memory management, task scheduling, and access to other hardware devices.
As well as the kernel, an operating system is often distributed with tools for programs to display and manage a graphical user interface, as well as utility programs for tasks such as managing files and configuring the operating system. They are also often distributed with application software that does not relate directly to the operating system's core function, but which the operating system distributor finds advantageous to supply with the operating system. The exact delineation between the operating system and application software is not precise, and is occasionally subject to controversy. For example, one of the key questions in the United States v. Microsoft antitrust trial was whether Microsoft's Internet Explorer web browser was part of its Windows operating system or if it was a separable piece of application software.
Like the term "operating system" itself, the question of what exactly should form the "kernel" is subject to some controversy, with debates over whether things like file systems should be included in the kernel. Various camps advocate microkernels, monolithic kernels, and so on as compromises.
Operating systems are used on many, but by no means all computer systems. The simplest computers, including the smallest embedded systems and many of the first computers did not have operating systems, and relied on the application programmer to manage the minimal hardware themselves, perhaps with the aid of libraries developed for the purpose. Commercially-supplied operating systems are present on virtually all modern devices described as computers, from personal computers to mainframes, as well as mobile computers such as PDAs and mobile phones.
An operating system is a special computer program that manages the relationship between application software, the wide variety of hardware that makes up a computer system, and the user of the system.
The lowest level of any operating system is its kernel, the first layer of software loaded into computer memory when a system boots, or starts up. The kernel then provides access to various common core services to all other system and application programs. These services include, but are not limited to: disk access, memory management, task scheduling, and access to other hardware devices.
As well as the kernel, an operating system is often distributed with tools for programs to display and manage a graphical user interface, as well as utility programs for tasks such as managing files and configuring the operating system. They are also often distributed with application software that does not relate directly to the operating system's core function, but which the operating system distributor finds advantageous to supply with the operating system. The exact delineation between the operating system and application software is not precise, and is occasionally subject to controversy. For example, one of the key questions in the United States v. Microsoft antitrust trial was whether Microsoft's Internet Explorer web browser was part of its Windows operating system or if it was a separable piece of application software.
Like the term "operating system" itself, the question of what exactly should form the "kernel" is subject to some controversy, with debates over whether things like file systems should be included in the kernel. Various camps advocate microkernels, monolithic kernels, and so on as compromises.
Operating systems are used on many, but by no means all computer systems. The simplest computers, including the smallest embedded systems and many of the first computers did not have operating systems, and relied on the application programmer to manage the minimal hardware themselves, perhaps with the aid of libraries developed for the purpose. Commercially-supplied operating systems are present on virtually all modern devices described as computers, from personal computers to mainframes, as well as mobile computers such as PDAs and mobile phones.
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