What is an Operating System?

What is an Operating System?

If we just build a computer, using its basic physical components, then we end up with a lot of assembled metal, plastic and silicon. In this state the computer is useless. To turn it into one of the most useful tools we need software. We need applications that allow us to write letters, write software, perform numerical modeling, calculate cash flow forecasts etc etc. But, if all we have are just the applications, then each programmer has
to deal with the complexities of the hardware. If a program requires data from a disc,the programmer would need to know how every type of disc worked and then be able to program at a low level in order to extract the data. In addition, the programmer would have to deal with all the error conditions that could arise. For example, it is a lot easier for a programmer to say READ NEXT RECORD than have to worry about: spinning the
motor up, moving the read/write heads, waiting for the correct sector to come around and then reading the data.It was clear, from an early stage in the development of computers, that there needed to be a “layer of software” that sat between the hardware and the software, to hide the user
from such complexities, and to hide the „breakable‟ parts of the computer from human error or stupidity. Thus we can define operating system as “It is the system software that acts as a interface between computer hardware and users and provides easy interface to the users by hiding underlying complexities of computer hardware “

Two views of an operating system

Now we are going to look at two views of an operating system. In another word we can categorize functions of an operating system into two categories

OS as Resource Manager:

 One view considers the operating system as a resource manager. In this view the operating system is seen as a way of providing the users of the computer with the resources they need at any given time. Some of these resource requests may not be able to be met (memory, CPU usage etc.) but, the operating system is able to deal with problems such as these. For example consider the situation where more than one process is requesting CPU. If we have single CPU it can be assigned to only one process at a time. OS is responsible for when to provide CPU to which process called CPU scheduling. Similarly other resources are also managed by CPU.

OS as Extended Machine:

Another view of an operating system sees it as a way of not having to deal with the complexity of the hardware. If we have operating system,we can read data easily from disc by issuing a command such as READ. But, if we don‟t have OS we have to deal with low level complexities f disc to read data from it.We should know whether the floppy disc is spinning, what type of recording method we should use, What error codes are used etc etc. Operating system hides all these complexities from us simple minded users and provides convenient interface. So in this view of the machine, the operating system can be seen as an extended machine or a virtual machine.