Which of the following is not an operating system? A. DOS B. Linux C. Windows D. Oracle

DOS
Linux
Windows
Oracle

The correct answer is D. Oracle.

An operating system is a software that manages computer hardware and software resources and provides common services for computer programs. It is a vital part of every computer system, and without it, the computer would not be able to function.

DOS, Linux, and Windows are all operating systems. DOS is a discontinued operating system that was developed by Microsoft in the 1980s. Linux is a free and open-source operating system that was developed in the 1990s. Windows is a proprietary operating system that was developed by Microsoft in the 1980s.

Oracle is a database management system (DBMS) that is used to store and manage data. It is not an operating system.