Humans do not have the ability to solve all problems, and even if they do, not as fast as a computer can do.A digital computer is a machine that follows algorithms written by humans.

Following an algorithm means solving a problem by carrying out instructions of how to solve it.The earliest electronic digital computers were launched in the 1940s. These machines had no operating system. The programs had to be entered one bit at a time on rows of mechanical switches.The language programs of the machine were entered on punch cards, and the programming process were speed by developing the assembly languages.The first Operating System was implemented in 1950s by the General Motors Research Laboratories.

The systems were called single - stream batch processing systems because the programs and data submitted were in groups or batches. An Operating System is the software that controls the hardware. The hardware includes processors, storage, Input/Output devices, communications devices and data.Hardware only specify the physical devices that a computer uses to accomplish a task, provides computer power, but cannot use it.

To make the power that the hardware provides useful, an Operating System is needed because it makes this power usable. Operating System, which are resource managers, manage the computer hardware and makes them conveniently available to the users.In a computer , the Operating System plays the main integral role, since many functions such as the user interface implementation, share of hardware among users, prevention of interference of a user with another, resource scheduling of users, allowance of data share among users, Input/Output facilitation, error recovery, resource usage accounting, parallel operation facilitation, secure and rapid data access organisation, and network communications handling.In comparison with the systems of 1950s the computers in 1960s were also batch processing systems, but they allowed multitasking, i.e. allowed to run several tasks at a time.

Moreover, they contained many peripheral devices such as printers, card punches, card readers, disk - and tape drives. Many of these time -sharing systems were multimode systems and they also supported batch processing as well as real-time applications. Real-time systems supply immediate response .Computer designers observed that some other job could use the idle processor, at the same time while it is used by a job for an Input/Output operation, so that it does not have to wait until the first one completes.

Considering this fact brought the Operating System designers to develop multiprogramming computers that will keep all the jobs in main memory at one go, and a processor is switched in between each job in order to keep them advancing, whereby the peripheral devices are in use.IBM announced its Systems/360 family of computers in 1964, and OS/360 that offered greater power. This architecture evolved over the years to the 370, and later to 4300 and 30X0 series.Although these systems were designed to perform basic interactivity for users with computers, they brought great offers to the program development environments, since these systems started to reduce the time taken between submitting a task and getting the result, to minutes or even seconds. This made programmers easier to write program codes and get the result immediately, as it was just compiling the program code, and if any errors, perform and immediate correction and recompile it. Programmers did not need to wait too long as it was the case with earlier systems.

The first major Operating System, written in high level language, unlike the earlier ones written in an assembly language, was called "Multics" and owned by MIT using CTSS system. The experience of this development made the designers to create the high level language C that was specifically created to implement UNIX.Moreover, concept of "virtual storage" that increased the actual size of primary storage, and thus enabling programs to address much larger amounts of memory, was incorporated by Multics, and two other systems called "TSS" and "CP/CMS". This incorporation has set the users free from memory management.In the 1970s, the experimental time-sharing systems of 1960s were evolved into solid commercial products.

Around this time, Personal Computers (PCs) and microprocessor technology started their early stage.The TCT/IP communications standards/protocols, which are still in use as the Internet protocol, became widely used mainly in military and universities, since the United States increased the communications between computer systems. In consideration of security problems that occurred, the concept of "encryption" of data became highly important.1980s was the time of the evolution of microprocessor technology. Through this time, most of the computers were single-processor systems.The aim of the hardware design was to have processors to perform as many instructions per second as possible, and the aim of the software design was to share that processor effectively among jobs in order to ensure maximum utilization.

Furthermore, because of the maximum usage of personal computers, desktop computers were built to enable users to work individually.To make the work much easier, application software programs such as word-processors, spreadsheets, database - and graphics packages were published. This took also an important part in the personal computer revolution.The use of computers increased and almost everyone was able to use one effectively.Computing became a distributed trend that allowed the execution of parcelled sub-computations on other processors, for example in computer networks, or other multiprocessor systems.Standards and protocols for open computing and communications systems were developed my organizations.

The term "open systems" defines the open, wide, and inexpensively licensed availability of computer systems.There was a new architecture in 1980s, called the "RISC" architecture, which was replacing the complicated "CISC" architecture. It was much simpler, but faster and these machines could execute multiple instructions at the same time, basically known as multitasking systems.The MS-DOS (DOS) and OS/2 Operating Systems were produced by IBM was supplied by Microsoft Corporation and in addition to this, the Intel company produced increasingly powerful Central Processing Units (CPUs).

Because the MS-DOS Operating System does not provide a Command Line Interface (CLI), IBM and Microsoft developed an Operating System with Graphical User Interface (GUI). This was because MS-DOS is provides only a Command Line Interface, which means you can only see white fonts in a black background, and you will only be dealing with commands that you have to understand and remember. Besides, without providing a GUI that would be easier for the user to work with, it was not user-friendly as well.In the meantime of this production, Microsoft developed its own Windows Operating System that was able to run on MS-DOS.The Windows Operating System provided a user-friendly Graphical User Interface, which brought Microsoft a huge success, since most of the people would want to prefer such an Operating System, instead of one where they have to remember all the commands.Apple Macintosh Computers were especially produced for graphical use, thus it had a GUI consisting of colour graphics.

There was no command to see on the user interface, everything was replaced by graphical menus and other features. But because Macintosh developers kept their computers as a closed system, hardware vendors did not get any chance to build system that would also run in Macintosh software application.Comparing Microsoft Windows Operating System with the Apple Macintosh's.. we can say that Windows has a similar interface like the Macintosh Computers, consisting of colour graphics and user-friendly features.

Hence, technology is moving forward in a rapid speed, new computer - and operating systems architectures evolved over the next few years.It was meant to be supporting the already existing major application bases.New architectures, such as MS-DOS, OS/2, and UNIX had the ability to support them also.In 1990s, there were six most important major Operating Systems in the computer industry, which were UNIX, MS-DOS, MVS, VM, the Macintosh Operating System and IBM's expected Mainframe Operating System.

Selected among these, the Operating Systems UNIX and MS-DOS are more considered by the hardware and software designers, because they support their own proprietary architectures.The most widely used Operating System in the world in MS-DOS, since it is able to support a massive base of software applications that thousands of software vendors worldwide supply.Today there is a lot more. Viewing the development of the Computer Architecture, there are many new architectures developed so far, and of course, there will be more to follow in future.Peoples' usage and interaction with computers is increasing in day to day basis, and designers are on their way to improve technology by developing newer and better architectures with more features and high speed.

The computer industry shows its success in architecture by the development of modern multimedia Personal Computers (PCs), Laptops - and Palmtop Computers, Flat Screen Computers, and so on.Taking a look back at the earlier computers, today's ones are more featured and easy to use, especially for "lay" people. Because the earlier Operating Systems like MS-DOS or UNIX had Command Line Interface, where users had to remember all the commands in order to use it. But today's Operating Systems provide Graphical User Interface that is understandable and easier to than the Command Line one. Working with in MS-DOS or UNIX also needs understanding of the commands that the user types in, because the user should be aware of what he wants the system to do and do his work with understanding, otherwise he will not be able to detect errors or solve the problems he might have get.

The Graphical User Interface in comparison, displays a pleasant atmosphere with the options of setting wallpapers and screensavers that one can select as per his or her wish, the desired atmosphere. It also provides easy task performance by containing colour graphics. The user just need to click on the images that indicates the program or task he wants the system to perform and it will open up for him. There is no need to remember commands.Furthermore, looking at the white fonts on a black background all the time will be boring and depressing as well, whereas in a Graphical User Interface you can see a lot more in colour.Bibliography ; ReferencesBooks:John L.

Hennessy ; David A. Patterson, "Computer Architecture a quantitative approach", 2nd Edition, 1996, published by Morgan Kaufmann Publishers, Inc, San Francisco, CaliforniaH. M. Deitel, "Operating Systems", 2nd Edition, 2000, by Pearson Education Asia Pte Ltd.Andrew S. Tanenbaum, "Structured Computer Organization", 4th Edition,1999, by Prentice Hall of India Private Ltd., New DelhiWebsites:http://www.armory.com 2050 Page 1 5/10/2007Gasthurie Kanagachandran 2035883