About : Operating System &
Ubiquitous Computing
How an Operating System Works :
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Operating System (OS), in computer science, the basic software that controls a computer. The operating system has three major functions: It coordinates and manipulates computer hardware, such as computer memory, printers, disks, keyboard, mouse, and monitor; it organizes files on a variety of storage media, such as floppy disk, hard drive, compact disc, digital video disc, and tape; and it manages hardware errors and the loss of data.
Operating systems control different computer processes, such as running a spreadsheet program or accessing information from the computer's memory. One important process is interpreting commands, enabling the user to communicate with the computer. Some command interpreters are text oriented, requiring commands to be typed in or to be selected via function keys on a keyboard. Other command interpreters use graphics and let the user communicate by pointing and clicking on an icon, an on-screen picture that represents a specific command. Beginners generally find graphically oriented interpreters easier to use, but many experienced computer users prefer text-oriented command interpreters.
Operating System :
Operating systems are either single-tasking or multitasking. The more primitive single-tasking operating systems can run only one process at a time. For instance, when the computer is printing a document, it cannot start another process or respond to new commands until the printing is completed.
All modern operating systems are multitasking and can run several processes simultaneously. In most computers, however, there is only one central processing unit (CPU; the computational and control unit of the computer), so a multitasking OS creates the illusion of several processes running simultaneously on the CPU. The most common mechanism used to create this illusion is time-slice multitasking, whereby each process is run individually for a fixed period of time. If the process is not completed within the allotted time, it is suspended and another process is run. This exchanging of processes is called context switching. The OS performs the “bookkeeping” that preserves a suspended process. It also has a mechanism, called a scheduler, that determines which process will be run next. The scheduler runs short processes quickly to minimize perceptible delay. The processes appear to run simultaneously because the user's sense of time is much slower than the processing speed of the computer.
Current Operating Systems :
Operating systems commonly found on personal computers include UNIX, Macintosh OS, and Windows. UNIX, developed in 1969 at AT&T Bell Laboratories, is a popular operating system among academic computer users. Its popularity is due in large part to the growth of the interconnected computer network known as the Internet. Software for the Internet was initially designed for computers that ran UNIX. Variations of UNIX include SunOS (distributed by SUN Microsystems, Inc.), Xenix (distributed by Microsoft Corporation), and Linux (available for download free of charge and distributed commercially by companies such as Red Hat, Inc.). UNIX and its clones support multitasking and multiple users. Its file system provides a simple means of organizing disk files and lets users control access to their files. The commands in UNIX are not readily apparent, however, and mastering the system is difficult. Consequently, although UNIX is popular for professionals, it is not the operating system of choice for the general public.
Instead, windowing systems with graphical interfaces, such as Windows and the Macintosh OS, which make computer technology more accessible, are widely used in personal computers (PCs). However, graphical systems generally have the disadvantage of requiring more hardware—such as faster CPUs, more memory, and higher-quality monitors—than do command-oriented operating systems.
Future Technologies :
Operating systems continue to evolve. A recently developed type of OS called a distributed operating system is designed for a connected, but independent, collection of computers that share resources such as hard drives. In a distributed OS, a process can run on any computer in the network (presumably a computer that is idle) to increase that process's performance. All basic OS functions—such as maintaining file systems, ensuring reasonable behavior, and recovering data in the event of a partial failure—become more complex in distributed systems.
Research is also being conducted that would replace the keyboard with a means of using voice or handwriting for input. Currently these types of input are imprecise because people pronounce and write words very differently, making it difficult for a computer to recognize the same input from different users. However, advances in this field have led to systems that can recognize a small number of words spoken by a variety of people. In addition, software has been developed that can be taught to recognize an individual's handwriting.
Sontaneous Information System :
A spontaneous information system is a system composed of computing devices that are carried by people and that communicate by a Short Distances Wireless (SDW) interface. Devices can only communicate with each other when they are within a relatively short distance. Since devices are mobile, a device may leave a network at any time – simply by being moved out of communication range of other devices. Spontaneous networks are analogous to human groupings: people can only directly communicate when they are close, strangers that meet may exchange information, and this exchange may lead to further exchanges (notably of more sensitive information) as the relationship develops. A person can find himself in a network at any time, and the network around him or her varies over time. It is very easy to imagine relevant applications of this paradigm: medical domain, e-commerce, PDA-to-PDA information exchange, games, etc.
Among all the challenges we have identified, we have selected some which demonstrate the real need for new research. One is coming from the fact that the network composition is dynamic and localized. Devices can only communicate with devices in their neighborhood, and once a device leaves the range of communication, it no longer forms part of that network. A device can only use the information available on its current network. The second one is autonomy. For instance, many spontaneous systems are formed mainly by PDAs, which are programmable devices. On the one hand, this makes the range of possible applications large. On the other hand, it introduces extra complexity since devices may interact in unforeseen ways. For example, a device may use a protocol that other devices are unaware of.
The last important feature of spontaneous systems is that the value of the information can be highly localized in time and place. For instance, information about a traffic jam can be useful to a person in a car who is one kilometer from the jam, but the information is useless one day later or to anyone who is not in a car. Information in a spontaneous network is highly contextual and situational.
All of these problems combined are particular to spontaneous information systems and suggest a new form of building and operating systems as the user’s physical mobility has to be taken into account at the resource management level (energy, CPU, etc). Currently we are involved in two main directions, one related to the proposal of predictive scheme in order to estimate the communication time depending on users’ mobility. The other is concerned with data location and accesses. In order to integrate all these results a demonstrator is under construction.
References :
----> Image of an andvance Operating System