An Operating System is the software which interacts with the hardware of a computer system and works as the intermediary between the installed applications and the hardware, including peripherals such as a printer, a computer mouse or a keyboard. When you run an application, it transfers requests to the OS using an API (Application Program Interface) and the contact is done via a command line or a Graphical User Interface (GUI). Similar to a personal computer, hosting servers also have an Operating System that acts as a host for all the software installed on them, which includes script applications or server-side software such as a flash server, a VOIP server, and so on. A virtual machine can be set up on a physical one, so it is possible to install a guest OS on it and have a different system environment in contrast to the physical server host OS.