Operating System
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.
Hardware functions such as input and output are managed by the OS. This includes anything from the keyboard to the mouse extremely complex devices such as the GPU. This input and output can even include system calls between programs running on the same computer.
Shell
A shell is a computer program that exposes an operating system's services to human users or external programs that automate an OS.
Linux
Linux is a popular open source operating system and the flagship software project of the .