An operating System is the way you communicate or operate your computer, therefore being called operating system. It by far is the most important program which runs on the computer. Not only on our desktops and laptops, but on palm tops, cell phones and pda’s, the operating system is present. The operating systems tasks are basic but extremely important like, recognizing input from the keyboard, sending output to the display screen, having a file allocation table in place where it stores the data consistently for ease of use for the user and also to control any external devices which are connected to the computer. You can call it as the Head of the House or a Decision Maker because the OS decides what the computer needs to progress like, most times by users commands but at times by malfunction of viruses.

Just like the head of the house, if the family is bigger, the more the responsibilities, and a similar case for operating systems as well. It needs to be handling more soft wares with a faster speed. We can also think of it as a traffic police, who makes sure that all the cars go in the same direction as they intend to go from that road, any deviation may be punishable. The operations system is similar, it makes sure that different programs and users running at the same time do not inter fear with each other. In cases of anti social elements, which disrupt the normal course of traffic, viruses work in the same manner for computers, and with some extra force, the computer’s security network ensures that these elements are derailed from their normal course, thus ensuring a safe computer.

Operating systems can be classified as follows:
1) Multi-User: Allows two or more users to run programs at the same time. Few operating systems allow thousands of concurrent users.
2) Multiprocessing: Supports running a program on more than one CPU.
3) Multitasking: Allows more than one program to run concurrently.
4) Multithreading: Allows different parts of a single program to run concurrently.
5) Real time: Responds to input instantly. General purpose of operating systems like UNIX and DOS are not real time.

We can use the example of a Road now to understand the functioning of programs and Operating System. Because there is a road, there are cars that run on it. Its only because of the smooth road, the car can run on it. When the road is rocky, or unstable the car can’t run smoothly and runs slowly as well. Same is the case of OS and Soft wares, where the Road is the OS and soft wares are the cars. If the OS is good without a virus, the soft wares will run properly, if there are problems, the soft wares will have problems. It also establishes the fact that software needs an operating system to run. Operating systems provides software platform on apex of other programs known as application programs. Application programs are to be written on the top to run that operating system. Your selection of operating system thus determines to huge extent to run the applications. The wellknown operating systems for PCs are OS/2, Windows, DOS but many others are available like Linux.