An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources.
For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer – from cellular phones and video game consoles to web servers and supercomputers.1
Linux is the world’s largest and most pervasive open source software project in the history of computing. The Linux kernel is the largest component of the Linux operating system and is charged with managing the hardware, running user programs, and maintaining the security and integrity of the whole system. It is this kernel which, after its initial release by Linus Torvalds in 1991, jump-started the development of Linux as a whole.2
FreeBSD is a free and open-source Unix-like operating system descended from Research Unix via the Berkeley Software Distribution (BSD). FreeBSD is a direct descendant of BSD, which was historically called "BSD Unix" or "Berkeley Unix" (in violation of the UNIX trademark). The first version of FreeBSD was released in 1993, and as of 2005 FreeBSD was the most widely used open-source BSD operating system, accounting for more than three-quarters of all installed BSD systems.3
MacOS is a series of graphical operating systems developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac family of computers. Within the market of desktop, laptop and home computers, and by web usage, it is the second most widely used desktop OS, after Microsoft Windows.4