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Topic: Preemptive multitasking

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	Computer multitasking - Wikipedia, the free encyclopedia
		Multitasking solves the problem by scheduling which task may be the one running at any given time, and when another waiting task gets a turn.
		Another reason for multitasking was in the design of real-time computing systems, where a number of possibly unrelated external activities needed to be controlled by a single processor system.
		Typically, a multitasking system allows another process to run when the running process hits a point where it has to wait for some portion of memory to be reloaded from secondary storage.
	en.wikipedia.org /wiki/Computer_multitasking (1478 words)

	Multitasking definition by The Linux Information Project (LINFO)
		In a multitasking system, however, multiple processes are retained in the main memory, which physically consists of RAM (i.e., random access memory) chips, so that whenever one process has to wait, the operating system can immediately allocate the CPU to other processes.
		Preemptive multitasking increases overall system efficiency by freeing up the CPU and other system resources when ordered to by the operating system on a time slice basis or a priority basis so that one application cannot monopolize system resources when they are needed by another program.
		Multitasking is particularly crucial for real time operating systems (such as are used in embedded systems), for which it is necessary to monitor and control multiple external activities with a single processor virtually instantaneously.
	www.bellevuelinux.org /multitasking.html (1290 words)

	Threads (Site not responding. Last check: 2007-11-05)
		In preemptive multitasking, on the other hand, a separate scheduling task is responsible for switching one process off and another one on.
		Preemptive multitasking avoids the problem of tasks with bugs consuming all the CPU time, since tasks are switched off from the outside.
		Preemptive multitasking is more reliable than cooperative multitasking, especially when developing and debugging a system, because the system will still run even though one or more tasks are in infinite loops.
	home.earthlink.net /~mcdemarco/QA/threads.html (1248 words)

	The Digital Research Initiative
		When an operating system is called a "preemptive multitasking operating system," it means that the computer is able to have all the coolest super-multitasking powers as a result of how the operating system is designed.
		As a rule, most computers are powerful enough to handle preemptive multitasking, at least those made since the mid-1980s, but usually these computers don't have that ability because of the limitations of their operating systems.
		It should be also noted that "preemptive multitasking" is an elusive goal for many operating systems, as very few are able to achieve this ability, Some companies claim their system is preemptive multitasking, when it is really not.
	www.ibiblio.org /team/intro/unix/what.html (785 words)

	creativepro.com - Multiprocessing in Mac OS X
		Preemptive multitasking, used in Mac OS X, actively manages access to the CPU, allowing one process to preempt another when needed.
		Preemptive threading, used in Mac OS X, allows a thread to preempt or interrupt another one that is active on a CPU.
		Preemptive multitasking and threading allow Mac OS X to be a truly symmetrical MP system.
	www.creativepro.com /story/news/10640.html (1111 words)

	[No title]
		Cooperative multitasking is where the application is given control and it is the application's responsibility to give up control so that other applications may execute.
		The move to a preemptive multitasking model represents a a significant departure from Windows 3.1.
		And while the resulting "hourglass" is expected under a cooperatively multitasked environment, it seems out of place in a "next generation" Windows that supposedly "preemptively multitasks" native Win32 applications.
	www.os2bbs.com /file_d/text/OS2VSCHG.TXT (3569 words)

	Pre-emptive multitasking - Wikipedia, the free encyclopedia
		Pre-emptive multitasking is sometimes mistakenly used when the intended meaning is more specific, referring instead to the class of scheduling policies known as time-shared scheduling, or time-sharing.
		Although multitasking techniques were originally developed to allow multiple users to share a single machine, it soon became apparent that multitasking was useful regardless of the number of users.
		Multitasking makes it possible for a single user to run multiple applications at the same time, or to run "background" processes while retaining control of the computer.
	en.wikipedia.org /wiki/Pre-emptive_multitasking (528 words)

	Get Started with Multithreading in .NET* - Printable Version (Site not responding. Last check: 2007-11-05)
		Preemptive multitasking differs from cooperative multitasking where each task decides how long it will execute.
		Preemptive multitasking prevents one task from taking up all the processor's time.
		Windows is a preemptive multitasking operating system, giving it the ability to appear to perform multiple tasks simultaneously.
	www-personal.engin.umich.edu /~fbartho/threads/multithread.html (2091 words)

	The Common Man's Guide to Operating System Design: Processes (Site not responding. Last check: 2007-11-05)
		A full discussion of multitasking and how it overcomes the limitations of single tasking is best accomplished by discussing, in turn, two implementations (though definitely not mutually exclusive of each other) of multitasking.
		Pre-emptive multitasking is by far the single most common design for modern operating systems, and probably the best, most reliable design except when compelling reasons point elsewhere.
		Also, when the only purpose of multiprogramming is to gain extra system performance, cooperative multitasking will typically do a better job of this than preemptive multitasking, at a considerable cost in system responsiveness and reliability.
	cdsmith.twu.net /professional/osdesign/ch04.html (6049 words)

	BeOS or NeXT: The Right Choice
		Multitasking is the ability to run more than one program at the exact same time.
		Preemptive multitasking is better in most circumstances, but let's look at both.
		If multitasking is running multiple applications at the same time, multithreading is running multiple parts of an application at the same time.
	www.lowendmac.com /myturn/010418.html (1885 words)

	Programming in Java
		Multitasking is the ability of a computer's operating system to run several programs (or processes) concurrently on a single CPU.
		In preemptive multitasking, the operating system decides how to allocate CPU time slices to each program.
		Examples of operating systems that support premptive multitasking are Unix, Windows 95/98, Windows NT and the planned release of Mac OS X. Cooperative multitasking.
	web.mit.edu /1.124/LectureNotes/Multithreading.htm (1164 words)

	Multitasking with microcontrollers
		Multitasking operating systems have become quite familiar lately, since Microsoft Windows(R) and Unix conquered the growing market of personal computers software.
		The "preemptive" multitasking uses a high priority interrupt, coming at regular, predetermined, time intervals to switch tasks.
		This problem is solved in the so called "supervised cooperative" multitasking, by introducing a watch dog timer, which forces task switching if a task lasts more than a specified amount of time.
	www.geocities.com /isusnea/mtask.html (1264 words)

	California Digital Corporation : DQ
		A technique called "backfill" is commonly used to achieve a better trade-off, however it requires users to provide accurate estimates of the computational time their jobs need, which is not usually available.
		However, in the absence of true preemptive multitasking, there were no equivalents for clusters.
		DQ is the first preemptive scheduler for distributed memory clusters and comes integrated with systems management software.
	www.californiadigital.com /dq.shtml (444 words)

	Dr. Dobb's \| A Non-Preemptive Multitasking Executive In C++ \| April 15, 2003
		I've presented an executive that is a multitasking, non-reemptive kernel with a cooperative scheduling discipline.
		A multitasking application is normally composed of several user tasks.
		This is not a complete executive, but it is a practical implementation using inheritance in a multitasking programming context.
	www.ddj.com /dept/cpp/184402255 (1373 words)

	POPULAR OPERATING SYSTEMS Windows 95
		However, if users want to do several things simultaneously, they are going to find that preemptive multitasking provides smoother operation and better speed.
		Preemptive multitasking means that one Windows application can get control of CPU without the knowledge of another Windows application.
		In contrast, Cooperative multitasking means that an application can assume it has full control until it yields to other applications.
	home.olemiss.edu /~misbook/sosw95s.htm (466 words)

	32-Bit Computing - What's It All About?
		Yet another advantage of 32-bit systems is faster multitasking, where two or more applications run at the same time.
		With cooperative multitasking, the operating system gives control to an application and it is the application's responsibility to release control.
		With preemptive multitasking, the operating system decides which application will receive control of the CPU and when it will release control.
	web.mit.edu /ist/isnews/v11/n02/41019.html (873 words)

	Managing Memory and Disks (Site not responding. Last check: 2007-11-05)
		In cooperative multitasking, the operating system gives each running application control of the system CPU, and the application is expected to relinquish the processor at frequent intervals.
		In preemptive multitasking, the system retains control of the multitasking process, allocating CPU time to running processes as needed.
		Preemptive multitasking results in a more stable and efficient operating environment.
	www.windowsitlibrary.com /Content/226/06/2.html (1696 words)

	Circuit Cellar - Digital Library - 101 Man-Willrich
		What a multitasking executive does is to periodically take control of the CPU and allow other tasks to run.
		A preemptive system is more powerful than a cooperative one because it’s easier to program and it enables tasks to run more fairly.
		µexec is a preemptive multitasking system, but to keep the code small, its tasks all have the same priority level.
	www.circuitcellar.com /library/print/1298/Man101/index.htm (777 words)

	Multithreading Applications - Windows NT Multithreaded Programming
		This strategy to share the CPU is called preemptive multitasking and is different from the multitasking that Windows 3.1 performs between applications.
		The latter variation is called non preemptive multitasking and relies on an application voluntarily relinquishing control to the operating system before letting another application execute.
		In a non preemptive multitasking scheme, the amount of time a task is allowed to run is determined by the task, whereas in a preemptive scheme, the time is determined by the operating system.
	www.cswl.com /whitepapers/multithreading.html (3119 words)

	AMD’s Multiple Threads, Multiple Cores, Multiple Gains: Part 1
		This sure seems like multitasking, but the fact is that the vast majority of computers can't multitask (in the strict sense of the word), all they can do is task switch—just like me.
		While the term multitasking may not be precisely correct for what a one-CPU computer does, the term is used in that way by most people and I shall do so also.
		Preemptive means simply that the OS is in charge of what programs get CPU time, how much time they get, and when they get it.
	www.devx.com /amd/Article/32533 (1409 words)

	[No title]
		Multitasking is the art of executing simultaneously several programs, or executing several lines of execution within the same program, which is called multithreading.
		In a preemptive multitasking situation, there are cases when you absolutely do not want a task to be interrupted.
		In essence, a critical section is an island of cooperative multitasking in a sea of preemptive multitasking.
	nouspikel.group.shef.ac.uk /ti99/tasks.htm (12254 words)

	ChannelWeb Encyclopedia
		Programs can be run simultaneously in the computer because of the difference between I/O and processing speed.
		In the days of mainframes only, multitasking was called "multiprogramming," and multitasking meant "multithreading." See multithreading.
		Find the latest news and information on multitasking from across the Channelweb Network of IT Web sites.
	www.channelweb.com /encyclopedia/defineterm.jhtml?term=multitasking (197 words)

	[No title] (Site not responding. Last check: 2007-11-05)
		The trick is to find the equivalent of "memory protection and preemptive multitasking." That is, the features that will be essential in the future, but that are very hard to add while still supporting existing software.
		Preemptive multitasking and protected memory are features that are at the very core and heart of a OS.
		Preemptive multitasking and protected memory required major sweeping changes at the very core of the OS.
	arstechnica.com /staff/fatbits.ars/2005/9/27/1372/p1 (6756 words)

	The Performance Edge: OS X Runs A Marathon While OS 9 Is Just Finishing Tying Its Shoes - OS X And The ...
		It is interesting to note that this occurred because the OS allows for Multitasking, not because of multithreading, which is not enabled in the Sorenson codec that ships with QuickTime.
		In OS 9.2 multitasking was available but the background application ground to a halt while the foreground scrolling was taking place.
		As such they show only one side of the multitasking and multithreading capability of OS X. They show what performance will be like if you push the system to its fullest.
	macspeedzone.com /archive/html/art/edge/misc/a/multitasking.html (1440 words)

	Introduction to Preemptive Multitasking - real-time operating system, RTOS, fixed priority scheduling
		The memory costs of using a preemptive scheduler include extra ROM for the system calls plus RAM for task-specific stacks.
		Mutexes are an effective means of preventing race conditions, but introduce the possibility of priority inversions.
		In certain kinds of applications, the use of preemptive scheduling can simplify the overall software design by allowing it to be broken into tasks, but the approach does have its tradeoffs.
	www.netrino.com /Publications/Glossary/Preemption.html (1198 words)

	Geneva FAQ
		Preemptive multitasking gives all processes an equal chance to get control on a regular basis.
		The advantage of preemptive multitasking is that if an application goes into an infinite loop or does something that is computationally intensive (like ray tracing) where it doesn't want to have to use the AES, the other applications won't get locked-out.
		The major reason Geneva's primary mode of multitasking is cooperative is for backward compatibility.
	www4.pair.com /gribnif/files/FAQ/genevafaq.html (728 words)

	Multitasking and Preemption (Site not responding. Last check: 2007-11-05)
		Threads implement preemptive multitasking, because one thread can preempt another if it has to handle an event — for instance, the window server can handle a key event while an application is running, by preempting the running application thread.
		Active objects implement non-preemptive multitasking within the context of a single thread, because each event must be completely handled by its RunL() before the next event on that thread can be handled.
		The 'cooperation' in cooperative multitasking is that one task has to say "I am now prepared for another task to run", for instance by using Yield() or a similar function.
	archive.devx.com /upload/free/bkchapters/symbian/303x0305.asp (1671 words)

	MacKiDo/Myths/MultiTasking
		What PC people are complaining about is that the Mac doesn't use preemptive multitasking it uses a hybrid preemptive/cooperative tasking model.
		While I wouldn't mind preemptive multitasking, all it means is that if I am doing this many things at once (with a few more things in the background), I'll get slightly better performance, and maybe better responsiveness.
		The fact is that most people that argue against the Mac because of "lack of Preemptive Multitasking", have never actually used the Mac.
	www.mackido.com /Myths/MultiTasking.html (1014 words)

	Applelinks - The MACINTOSH Portal!
		Mac OS X, on the other hand, features protected multitasking, in which the operating system constantly monitors and allocates processor power to the various running applications as needed, balancing and sharing supply and demand, so to speak.
		Happily, when you run non-carbon legacy applications in the Classic environment under OS X, they benefit from preemptive multitasking as well, since Classic Mode runs as an application thread in OS X, and while they will still rely on cooperative multitasking when in Classic mode, a crash will not bring the entire system down.
		Preemptive multitasking gets addictive pretty quickly, and it is a great feeling to be able to send an application performing a process into the background knowing that it will run and more than a snail's pace.
	www.applelinks.com /articles/2002/01/20020123135926.shtml (1388 words)

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