Polling also refers to the situation where a device is repeatedly checked for readiness, and if it is not, the computer returns to a different task.
For example, polling a parallel printer port to check whether it is ready for another character involves examining as little as one bit of a byte.
That bit represents, at the time of reading, whether a single wire in the printer cable is at low or high voltage.
Polling can be employed in various computing contexts in order to control the execution or transmission sequence of the elements involved.
For example, in multitasking operating systems, polling can be used to allocate processor time and other resources to the various competing processes.
Although polling can be very simple, in many situations (e.g., multitasking operating systems) it is more efficient to use interrupts because it can reduce processor usage and/or bandwidth consumption.
[1] In star networks, which, in its simplest form, consists of one central switch, hub, or computer that acts as a conduit to transmit messages, polling is not required to avoid chaos on the lines, but it is often used to allow the master to acquire input in an orderly fashion.