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Topic: Cooperative multitasking

	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/Co-operative_multitasking (1478 words)

	multitasking from FOLDOC
		Under "cooperative multitasking" the running task decides when to give up the CPU and under "pre-emptive multitasking" (probably more common) a system process called the "scheduler" suspends the currently running task after it has run for a fixed period known as a "time-slice".
		Multitasking introduces overheads because the processor spends some time in choosing the next job to run and in saving and restoring tasks' state, but it reduces the worst-case time from job submission to completion compared with a simple batch system where each job must finish before the next one starts.
		Multitasking also means that while one task is waiting for some external event, the CPU to do useful work on other tasks.
	www.instantweb.com /foldoc/foldoc.cgi?multitasking (360 words)

	Operating Systems - Multitasking
		Multitasking is the process of letting the operating system perform multiple task at what seems to the user simultaniously.
		Multitasking is, on single-processor machines, implemented by letting the running process own the CPU for a while (a timeslice) and when required gets replaced with another process, which then owns the CPU.
		Preempetive multitasking moves the control of the CPU to the OS, letting each process run for a given amount of time (a timeslice) and then switching to another task.
	www.theorphys.elte.hu /fizinf/OpRendszerek/multitasking.html (1452 words)

	Multitasking definition by The Linux Information Project (LINFO) (Site not responding. Last check: 2007-11-05)
		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)

	epowiki: Cooperative Multitasking
		A form of multitasking where it is the responsibility of the currently running task to give up the processor to allow other tasks to run.
		The advantage of cooperative multitasking is that the programmer knows where the program will be descheduled and can make sure that this will not cause unwanted interaction with other processes.
		Thus cooperative multitasking can have lower overheads than pre-emptive multitasking because of the greater control it offers over when a task may be descheduled.
	www.possibility.com /epowiki/Wiki.jsp?page=CooperativeMultitasking (209 words)

	cooperative multitasking (Site not responding. Last check: 2007-11-05)
		Cooperative multitasking requires the programmer to place calls at suitable points in his code to allow his task to be descheduled which is not always easy if there is no obvious top-level main loop or some routines run for a long time.
		Under pre-emptive multitasking, the scheduler must ensure that sufficient state for each process is saved and restored that they will not interfere.
		Cooperative multitasking is used in RISC OS, Microsoft Windows and Macintosh System 7.
	burks.brighton.ac.uk /burks/foldoc/34/25.htm (216 words)

	[No title]
		A multitasking operating system should provide some degree of protection of one task from another to prevent tasks from interacting in unexpected ways such as accidentally modifying the contents of each other's memory areas.
		The processors may either communicate in order to be able to cooperate in solving a problem or they may run completely independently, possibly under the control of another processor which distributes work to the others and collects results from them (a "processor farm").
		Multithreading can thus be used for very fine-grain multitasking, at the level of a few instructions, and so can hide latency by keeping the processor busy after one thread issues a long-latency instruction on which subsequent instructions in that thread depend.
	www.cs.umb.edu /~dgebru/courses/cs310/hw10/doc.txt (1402 words)

	Multitasking :: Multi Tasking (Site not responding. Last check: 2007-11-05)
		Multitasking should not be confused with multiprocessing because this usually implies that more than a single CPU is performing the task or tasks.
		In multitasking only a single CPU performs the tasks, switching between the tasks and giving the impression that the tasks are being performed simultaneously, which in effect they are, but by switching rapidly from one task to the other rather than actually performing them simultaneously.
		Preemptive multitasking is where the operating system the CPU decides how to apportion time between the two (or more) tasks, whereas cooperative multitasking is where the programmes control the CPU, using up time until the task is executed.
	www.multitasking.co.uk (305 words)

	32-Bit Computing - What's It All About?
		With cooperative multitasking, the operating system gives control to an application and it is the application's responsibility to release control.
		So with cooperative multitasking, a wayward program can monopolize your machine and even bring it to a halt.
		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)

	Threads (Site not responding. Last check: 2007-11-05)
		In cooperative multitasking, the active task is responsible for switching itself off so that another task can use the CPU temporarily.
		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 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)

	[No title] (Site not responding. Last check: 2007-11-05)
		It's Apple's 'cooperative' multitasking, a form of > multitasking (albeit a less elegant one).
		a much easier way to handle multitasking is to have all the programs switch their own contexts out periodically.
		the type of multitasking you use also relates to the way your OS passes input to a program, and there are two ways of doing that, too.
	www.yawp.com /mike/posts/tech.04.txt (1452 words)

	POE: Poe documentation/Style Glossary (Site not responding. Last check: 2007-11-05)
		A form of multitasking where the programs themselves decide when to end their timeslices and allow other programs the chance to run.
		Cooperative multitasking can be dangerous because a single thread or process can hold a timeslice indefinitely.
		Multitasking is the fine art of dividing up a linear stream of time between two or more tasks.
	poe.perl.org /?Poe_documentation/Style_Glossary (2479 words)

	creativepro.com - Multiprocessing in Mac OS X
		Cooperative multitasking, used in Mac OS 9, is a scheduling method where each active process gets access to the CPU only if other processes allow it.
		In a cooperative environment, the second process must wait for the active one to yield the CPU, even though the active process isn't really using the processor.
		Similarly, in cooperative threading, the system, through its thread manager, schedules one thread to a processor for a fixed time, then the next one, and so on in a round robin.
	www.creativepro.com /story/news/10640.html (1111 words)

	System Abstraction Layer (Site not responding. Last check: 2007-11-05)
		Multitasking interface requires high effective inline implementations for critical sections (since this operations are very frequently used in multithreaded applications).
		Multitasking model of two other implementations depends on type of multitasking supported by concrete operating system for system threads.
		As far as cooperative multitasking provided by SAL is not visible for the system and debugger, a number of special functions were implemented to make it possible to debug such applications using standard debugger (debugger should support evaluation of user functions).
	www.ispras.ru /~knizhnik/SAL/ReadMe.htm (3216 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 "cooperative" method of switching tasks gives total control of system resources to every task, but requires the programmer to avoid infinite loops, or excessive time consuming routines, which will result in a system crash.
		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)

	Programming in Java
		Multitasking is the ability of a computer's operating system to run several programs (or processes) concurrently on a single CPU.
		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.
		This means that a program must cooperate in yielding control to other programs, or else it will hog the CPU.
	web.mit.edu /1.124/LectureNotes/Multithreading.htm (1164 words)

	cooperative multitasking (Site not responding. Last check: 2007-11-05)
		A form of multitasking in which all running applications must work together to share system resources.
		The operating system supports cooperative multitasking by maintaining a list of the active applications and the order in which they execute.
		A cooperative multitasking system differs from a preemptive multitasking system, in which the operating system executes each application in turn for a specific period of time (depending on priority) before switching to the next application, regardless of whether the applications themselves return control to the operating system.
	www.coffeycountyks.org /Terms/2461HTML-618.html (108 words)

	Geneva FAQ
		Cooperative multitasking relies on applications making certain calls frequently (in this case, AES calls) in order to allow the other processes a chance to become active.
		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 (Site not responding. Last check: 2007-11-05)
		The other form of multitasking is cooperative multitasking.
		Cooperative multitasking is when the OS gives the program full control of the CPU.
		With cooperative multitasking, the current process or task has complete control and will not allow any other processes to interrupt.
	www.newton.dep.anl.gov /askasci/comp99/CS027.htm (396 words)

	EUforum - Re: Multitasking (Site not responding. Last check: 2007-11-05)
		We have multitasking in E now released as inner property of E interpretator.
		Multitasking works the same in the interpreter and the translator, on all platforms (DOS, Windows, Linux, FreeBSD).
		With Euphoria's cooperative multitasking, there is far less danger, and less need for locks, since a task need not let go of control until it has completed a complete, logical step.
	www.listfilter.com /EUforum/m10588.html (223 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.
		Non-preemptive multitasking is not at all the same thing as cooperative multitasking.
		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)

	What is cooperative multitasking? - A Word Definition From the Webopedia Computer Dictionary
		A type of multitasking in which the process currently controlling the CPU must offer control to other processes.
		It is called cooperative because all programs must cooperate for it to work.
		Versions 8.0-9.2.2 of Macintosh OS and Windows 3.x operating systems are based on cooperative multitasking, whereas UNIX, Windows 95, Windows NT, OS/2, and later versions of Mac OS are based on preemptive multitasking.
	www.webopedia.com /TERM/C/cooperative_multitasking.html (116 words)

	[No title]
		There are two forms of multitasking: cooperative and preemptive.
		The Mac currently uses cooperative multitasking, in which background tasks get CPU time only when foreground tasks experience idle time and agree to release control to the background tasks.
		Cooperative multitasking works smoothly only if the programs actually cooperate with each other, and many do not.
	komar.cs.stthomas.edu /qm425/veng3.htm (807 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.
		With cooperative multitasking, each task decides when it's time to switch, and does so by returning control to a scheduler, which sets up the next task.
		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)

	BeOS or NeXT: The Right Choice
		Multitasking is the ability to run more than one program at the exact same time.
		Mac OS 8 and Windows 3.1/95/98/Me use cooperative multitasking (Windows 3.1/95/98/Me use preemptive multiprocessing to switch between DOS sessions, but we will ignore that for now).
		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 (1901 words)

	PIC specific Multitasking
		Note that task switching is very different from the switch statement used in the C language.
		For small systems where the programmer has complete control of every task, cooperative multitasking can be superior to pre-emptive multitasking.
		More complicated cooperative multitasking routines allow a task to return to the task scheduler before the end of it's main loop, and (once the task scheduler has run a few other routines) resumes executing right where it left off in that main loop.
	www.piclist.com /techref/microchip/multitasking.htm (3015 words)

	Managing Memory and Disks
		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.
		Because the operating system is always in control of the multitasking process, processor-greedy and hung applications cannot dominate CPU time, and all running applications receive the CPU time they require.
	www.windowsitlibrary.com /Content/226/06/2.html (1696 words)

	ASPN : Python Cookbook : simple, cooperative multitasking using generators (Site not responding. Last check: 2007-11-05)
		Cooperative multitasking offers an alternative to using threads.
		This recipe shows how to use generators to achieve simple, cooperative multitasking, that allows thousends of 'simultaneously' running tasks.
		This style of cooperative threading can be very useful.
	aspn.activestate.com /ASPN/Cookbook/Python/Recipe/466008 (249 words)

	Chapter 13 -- Getting Back on the Network (Site not responding. Last check: 2007-11-05)
		Cooperative multitasking was introduced on the Macintosh with System 7.0.
		When designing multitasking code with critical sections and synchronization mechanisms, be careful to avoid a condition referred to as deadlock (also known as the "deadly embrace").
		Multitasking is an essential part of modern operating systems such as Windows.
	osl.cpe.ku.ac.th /documentations/book/Netscape_plugin/ch13.htm (5614 words)

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