Define Virtual Storage System In Computer Systems And Also Define Advantage and Disadvantages

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This system uses the Virtual storage to enhance the capacity of computer. Virtual storage, as the name itself suggests is non-existing primary storage. It is just an Illusion of primary storage, which taken as ultimate for the all practical purposes. This illusion is generated, maintained and managed by computer system with the help of combination of hardware and software techniques. This concept of virtual storage removes the limitation of primary storage to hold programs which are being executed. As we have already seen that the execution of any program, it has to be loaded into the real primary storage.
It is sufficient to have part of the program which has to be executed, in the primary memory at any given point of time. The virtual storage on the basis, where it emphasis on storing only those instructions in the primary storage which are currently being executed and the other part of Secondary storage devices like hard disk, magnetic tapes etc. This is important because we cannot really expand the capacity of primary storage, as it is very costly affair. Therefore, we used it to the unavoidable extent and for other purposes we use less expensive secondary storage media.
The principle applied here is that the required part of the program is swapped between secondary memory and primary storage. This task is accomplished by the virtual storage system, where the program to be executed is divided into pages of same size, usually about 4 KB. The operating system swaps these pages between primary memory and secondary memory as an when required. This system makes it is a must that, only that page of program, which is being executed currently is stored in the primary memory and other pages are stored in the secondary storage. To keep track of these pages in the storage area, the operating system maintain tables which will make it convenient for CPU to locate these pages in the memory. Thus making it possible to execute multiple programs simultaneously with normal primary storage capacity.

Advantage of Virtual Storage System

The basic advantage of virtual storage system is that the capacity of the CPU can be utilized to fullest extent, as the pages of many programs can reside in the primary memory and secondary memorywhich are kept as and when required, thereby decreasing the size constraint of primary memory. The other major advantage is that the programmers now are received of the fear of size while writing the code for code for programs. Thus the problem of memory constraint for any program is reduced.

Disadvantage of Virtual Storage System

When advantages are there, it is obvious that disadvantages are bound to be there. The disadvantages of the virtual storageare that the overhead costs increase, the CPU time has to be devoted for swapping the pages between the primary and secondary memory. There is also a chance for thrashing, when one or more pages of a program except frequently and even the structure of the program can be caused thrashing.
Thus the operating systems help a programmer and to user to get this tasks done by providing him with an environment, which allowed him to program his tasks, without bothering about what has to be done in the background. These operating systems come as boon, to the user as the programmer by providing him a tension and hassle free work environment, which increases his productivity.

 

Basing on the features of the operating system programming and the interface providing they can be classified as:
User-friendly Operating Systems: Operating system which provide a pleasant and easy to work environment, where one need not really know much about the programming part, one can just keep on working with the various options, which are self explanatory. These operating systems are usually graphical based, where the various options are represented as icons, menus etc, with the choice to select from with these types of operating systems are need not know anything about computers with common sense he can work with the computer. Window 95, Window 98, Windows-NT are some of the of the user friendly operating systems. We will look into these operating systems later.

 

Programmer Friendly Operating systems: The programmer is anyone-who has fair knowledge about programming concepts and he is expected to know the working of a computer in a detailed manner. The programmer is usually not concerned with how an interface of the operating system is. He is much concerned about various utilities, functionalities, flexibility and very powerful environment to work in. He would like the operating system to be very flexible and give him an easy programming environment. It is well and good if it is a graphical interface, but even if the interface is character mode, if it is powerful, the programmer will prefer it. UNIX, XENIX, LINUX etc are some of the character based interfaces which are very powerful and are programmer friendly.
As we have already discussed about interfaces like Graphical User Interface (GUI) and Character User Interface (GUI) we will now look into these interfaces in detail as they play a major role in any application, operating system etc.

 

Character User Interface (GUI): This user interface as the name suggests is character based. Here one gets prompts in characters and a user has to type the characters. These were the interfaces which enabled the programmers to do their tasks easily, but they were bit difficult to work in as we have to type every instruction and commands as well these interfaces are not that pleasant to look at. Because, they powerful, the programmers looked forward to these interfaces. As there are almost no graphics involved these interfaces are relatively faster and the applications can be loaded within no time.
Earlier, even the application programs were character based, but they are now shifting towards graphic based as they are very pleasant and attractive as well easy to operate. Most of the earlier operating systemsas well current day operating systems are character based. They provide for graphics design environment, but they are not graphic based. MS-DOS, UNIX, LINUX etc are some of the most popular character based operating systems.

Graphical user Interface: As the name suggests, the user interface is graphical i.e., there are pictures, graphical objects, images, and menus etc, which have specific functionalities. Popularity known as GUIs these interfaces provide on user with a very pleasant environment 10 works in. Here almost every action is automated, at click of a button one can get the desired action done. These are the interfaces, which everyone looks forward to as they are not only pleasant, but are self explanatory, so that one need not have any knowledge about the system, but can still work with a great ease. Most of the applications are graphical based, so that one just learns the applicant and is able to carry on his tasks without learning programming part, as it is difficult task for the skill level to come up. Windows 95, Windows 98, Windows-NT are some of the very popular GUI based operating systems.

MOHIT BHARDWAJ

Hello Visitors, myself Mohit Bhardwaj working in blogging sector since last 8 years. my qualification in bachelor degree in computer science steam. contact Number: 80910-51002

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