Entry 1 :The Definition of Operating System

            Defining an operating system isn't a simple nor an easy task.
By simple, I mean this discussion takes place in various places, such as college classrooms to college campus (after finishing the classroom discussion with "lets take this "outside", that might give you the idea.).
And that's not all, defining OS takes place even in courtrooms. (See the "Interesting History" .)

Anyways, here is my attempt:

            An OS is a collection of programs (or "modules" in nerd-speak), that manages and controls the resources of a computer, or other computing device and gives user, and programs an interface to utilize these resources.
According to Linus Torvalds, the major creator of Linux, "An OS is a resource allocator."

            However, in general, there is no universally accepted definition for an OS. ( I really am not sure, what computer scientists have been doing since last 70 years or so, but I think that as usual some government should be blamed for this issue as well.)

            In the early days of computing, the ancestors of operating systems, "monitor programs" were created for only one purpose. And even today, it is purpose of the OS: to provide an environment in which a user can execute program(s).

            So, one view of OS focuses on the to control various Input/Output devices. (that's what I/O will stand for hereafter, I'll not try to divide a letter with zero.) The OS also controls the execution of programs to prevent errors and improper use of the computer. (here, with "preventing improper use", I mean using the computer hardware as as efficiently as possible. That means, OS will not mind you enjoying "Baywatch" on your computer, and that also means that you can stare at Yasmeen Bleeth as long as you want.)

            The fundamental goal of an entire computer machine/system is to execute user program(s) and make the problem solving easier, and towards this goal computer hardware is created. Since the bare hardware is not particularly is to use, application programs are created. These programs require certain common operations, such controlling I/O devices. The common functions of controlling and allocating resources are then brought together into one piece of software: the operating system.

            There is no universally accepted definition of what is the part of the OS and what isnt. (ok, now really is the time for some government to be blamed.) The most common definition is that the OS is the one program running at all the the times on the computer (unless if it is turned off, obviously)(this program is usually called as a kernel), with all else being application programs. This definition is the one which is generally followed.
And this is the very definition that I follow.