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Event Flag
{{notability, date=March 2019 An event flag is a process synchronization primitive in the OpenVMS operating system. It has two possible states, ''set'' or ''cleared''. The following basic primitive operations are provided: * Set event flag ($SETEF) * Clear event flag ($CLREF) * Wait for event flag ($WAITFR)--if the flag was clear, this would make the process wait until it was set. If the flag was already set, this would immediately return, leaving the flag set. Additional synchronization operations are: * $WFLOR--wait for any of the specified event flags to be set. * $WFLAND--wait for ''all'' the specified event flags to be set. Event flags can be either ''local'' (per-process) or ''common'' (accessible by more than one process). Each process has its own set of 64 local flags, numbered 0-63. It is also possible to ''associate'' the process with up to 2 sets of common event flags. These come in sets of 32 each, and the process can assign them numbers 64-95 or 96-127. They come i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synchronization
Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronous or ''in sync''—and those that are not are '' asynchronous''. Today, time synchronization can occur between systems around the world through satellite navigation signals and other time and frequency transfer techniques. Navigation and railways Time-keeping and synchronization of clocks is a critical problem in long-distance ocean navigation. Before radio navigation and satellite-based navigation, navigators required accurate time in conjunction with astronomical observations to determine how far east or west their vessel traveled. The invention of an accurate marine chronometer revolutionized marine navigation. By the end of the 19th century, important ports provided time signals in the form of a signal gun, flag, or dropping time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OpenVMS
OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using OpenVMS include banks and financial services, hospitals and healthcare, telecommunications operators, network information services, and industrial manufacturers. During the 1990s and 2000s, there were approximately half a million VMS systems in operation worldwide. It was first announced by Digital Equipment Corporation (DEC) as VAX/VMS (''Virtual Address eXtension/Virtual Memory System'') alongside the VAX-11/780 minicomputer in 1977. OpenVMS has subsequently been ported to run on DEC Alpha systems, the Itanium-based HPE Integrity Servers, and select x86-64 hardware and hypervisors. Since 2014, OpenVMS is developed and supported by VMS Software Inc. (VSI). OpenVMS offers high availability through clustering — the ability to distribute the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semaphore (programming)
In computer science, a semaphore is a variable or abstract data type used to control access to a common resource by multiple threads and avoid critical section problems in a concurrent system such as a multitasking operating system. Semaphores are a type of synchronization primitive. A trivial semaphore is a plain variable that is changed (for example, incremented or decremented, or toggled) depending on programmer-defined conditions. A useful way to think of a semaphore as used in a real-world system is as a record of how many units of a particular resource are available, coupled with operations to adjust that record ''safely'' (i.e., to avoid race conditions) as units are acquired or become free, and, if necessary, wait until a unit of the resource becomes available. Semaphores are a useful tool in the prevention of race conditions; however, their use is not a guarantee that a program is free from these problems. Semaphores which allow an arbitrary resource count are calle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System Technology
Operation or Operations may refer to: Arts, entertainment and media * ''Operation'' (game), a battery-operated board game that challenges dexterity * Operation (music), a term used in musical set theory * ''Operations'' (magazine), Multi-Man Publishing's house organ for articles and discussion about its wargaming products * ''The Operation'' (film), a 1973 British television film * ''The Operation'' (1990), a crime, drama, TV movie starring Joe Penny, Lisa Hartman, and Jason Beghe * ''The Operation'' (1992–1998), a reality television series from TLC * The Operation M.D., formerly The Operation, a Canadian garage rock band * "Operation", a song by Relient K from '' The Creepy EP'', 2001 Business * Business operations, the harvesting of value from assets owned by a business * Manufacturing operations, operation of a facility * Operations management, an area of management concerned with designing and controlling the process of production Military and law enforcement ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
