An Operating System, also known as an OS, is the software that makes a computer usable. The kernel is merely the “core” or lowest level of an operating system. The kernel provides numerous callable routines that allow other software to access files, display text and graphics, get input from a keyboard or mouse, and other such capabilities.
The operating systems that we come across today, generally have many features which are not the necessary features to make a system work. But these features are required to make the interaction with the system easier. Such features include graphical interface, file management, process management, shell, etc.
These features rely on the core part of the OS (called as kernel) to run and provide interface to the user or other application programs. It is to be realized that these features are inevitable, and only a kernel alone is of no use to the user.
An operating system also includes utilities that use the kernel. For example, MS-DOS provides a program known as COMMAND.COM, which is the program that allows a human to use the operating system. Windows Explorer, the MacOS Finder, and the various UNIX shells offer similar functionality. Other OS utilities may include a file manager, a software installer, and other items that are necessary to make the computer useful.