Are polling and event-driven programming different words for the same technique?

listener interrupt interrupt-handling event-driven-design
Niklas R. picture Niklas R. · Nov 26, 2012 · Viewed 8k times · Source

I studied interrupts vs cyclical polling and learnt the advantages of interrupts that don't have to wait for a poll. Polling seemed to me just like event-driven programming or at least similar to a listener and what the polling does is actually much like listening to input or output. Do you agree or did I misunderstand any crucial difference between polling (cyclical listening) and event-driven programming (also listening with so-called listeners)?

Answer

Lie Ryan picture Lie Ryan · Nov 26, 2012

Nope, quite the contrary interrupt driven programming is pretty much what event driven programming is at the hardware level. Both interrupt driven code and event driven code waits for event before running a code, while polling will attempt to query for event whether or not one actually exists.

However, it should be noted that interrupt- and event-driven programs are generally implemented in the lower level using a form of polling; there is no truly interrupt or event driven system that does not involve some sort of polling, although usually in hardware. In the case of interrupts, the CPU actually polls the interrupt line every clock cycle, and likewise with event driven programming because restarting a paused thread involves an interrupt being raised by the source of event (usually drivers).

You can say that interrupt- and event- driven programming is a disciplined way to poll that have lots of advantage compared to actually doing polling yourself.

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