Operating Systems

Abstract

This chapter discusses operating systems. The operating system of a computer is software, which controls all the computer's resources and provides the base upon which the application programs can be written. Modern operating systems also provide numerous services, such as inter-process communication, file and directory systems, data transfer over networks, and a command language for invoking and controlling programs. The operating system puts a layer of software on top of the bare hardware, manages all parts of the system, and presents the user with an interface or virtual machine that is easier to understand and program. An operating system thus can be defined as a set of software extensions of primitive hardware, culminating in a virtual machine that serves as a high-level programming environment and manages the flow of work in a network of computers. The virtual machine visible to the user is only the outermost of a series of software layers refining the base hardware. The principle behind the layered architecture is called information hiding—confining the details of managing a class of “objects” in a module that has a friendly interface with its users.