INTERRUPT HANDLER

Domain	Definition
Computing	Interrupt handler A routine which is executed when an interrupt occurs. Interrupt handlers typically deal with low-level events in the hardware of a computer system such as a character arriving at a serial port or a tick of a real-time clock. Special case is required when writing an interrupt handler to ensure that either the interrupt which triggered the handler's execution is masked out (inhibitted) until the handler is done, or the handler is written in a re-entrant fashion so that multiple concurrent invocations will not interfere with each other. If interrupts are masked then the handler must execute as quickly as possible so that important events are not missed. This is often arranged by splitting the processing associated with the event into "upper" and "lower" halves. The lower part is the interrupt handler which masks out further interrupts as required, checks that the appropriate event has occurred (this may be necessary if several events share the same interrupt), services the interrupt, e.g. by reading a character from a UART and writing it to a queue, and re-enabling interrupts. The upper half executes as part of a user process. It waits until the interrupt handler has run. Normally the operating system is responsible for reactivating a process which is waiting for some low-level event. It detects this by a shared flag or by inspecting a shared queue or by some other synchronisation mechanism. It is important that the upper and lower halves do not interfere if an interrupt occurs during the execution of upper half code. This is usually ensured by disabling interrupts during critical sections of code such as removing a character from a queue. (1994-10-27). Source: The Free On-line Dictionary of Computing.
Source: compiled by the editor from various references; see credits.

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Anagrams: INTERRUPT HANDLER

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "a-d-e-e-h-i-l-n-n-p-r-r-r-t-t-u"
	-4 letters: interplanted, intrapreneur.
	-5 letters: interdental, interrupted, interrupter, pentlandite, philanderer, turpentined.
Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro.