An operatingsystem is an organized collection of software extensions of hardware, consisting of control routines for operating a computer and for providing an environment for execution of programs.
H. M. Deitel
Operating systems are primarily resource managers; the main resource they manage is computer hardware in the form of processors, storage, input/output devices, communication devices and data. Operating systems perform many functions such as implementing the user interface, sharing hardware among users, allowing users to share data among themselves, preventing users from interfering with one another, scheduling resources among users, facilitating input/output, recovering from errors, accounting for resource usage, facilitating parallel operations, organizing data for secure and rapid access, and handling network communications.
A. Silberschatz , J. Peterson and P. Galvin
An operatingsystem is a program that acts as an intermediary between a user of a computer and the computer hardware.
An operatingsystem is similar to a government. The components of a computer system are its hardware, software, and data. The operatingsystem provides the means for the proper use of these resources in the operation of the computer system. Like a government, the operatingsystem performs no useful function by itself. It simply provides an environment within which other programs can do useful work.
William S. Davis
The operatingsystem is a set of software routines that sits between the application program and hardware. Because the operatingsystem serves as a hardware/software interface (Fig. 1.2 ), application programmers and users rarely communicate directly with the hardware.