An Operating System is the fundamental software that manages a computer. It controls how the hardware operates, the communication with peripherals like a monitor, a printer or a keyboard, the allocation of memory between various applications, as well as the prioritization of apps if multiple ones run at the same time. Any program that's installed on a notebook or a desktop operates by sending requests to the OS for different services by using an application program interface (API). The contact with the OS can be performed through a Graphical User Interface (GUI) or a command line. In the Internet hosting field, the Operating System is what runs a hosting server and all of the software installed on it, which includes not only website scripts, but also any other application such as a VOIP or a game server. If there are virtual machines created, they use a guest OS that is run on the server host OS.
