Saturday, February 21, 2009

Operating System Structure Part-1

If a system is large as well as complex then it is required that it must be designed carefully so that it can function properly and can be modified easily.The most common approach to achieve this is to partition the whole system into small components rather than having a single big structure.Now there are four approaches for achieving this.In this post we take a look at the first approach for structuring the system i.e Simple Structure.

Simple Structure:As all we know that every commercial system do not have well defined structure,the main reason behind this is,initially when these system are developed they developed as a simple,small,having limited functionality and then with time they started to grew up beyond their scope.The most common example of such type of a commercial system is MS-DOS.Initially when it was written the designers of DOS have no idea that this operating system became so popular in future.The main aim of designing this MS-DOS is to provide each and every functionality in a very limited space.So,in achieving this it was not divided into modules carefully.

In MS-DOS,the interfaces and level of functionality are not well separated.The major drawback of this thing is that application programs are able to access the basic I/O routines that means they can directly read or write to the basic display and disk drives.Due to this problem,the MS-DOS is very much vulnerable to the malicious programs,causing entire system crashes on the failing of user program.The other major problem with MS-DOS is that it is limited to hardware of its era because at that time the Intel 8088 for which it was written provides no dual mode and no hardware protection.Hence,in short we can say that their exists a lot of problem with this simple structure.