When a device sends an interrupt to the CPU, the CPU must identify the interrupting device.
In a system where there are many devices on an interrupt line, the CPU requires to identify which device has interrupted. It does this by querying each device in turn, asking if they are the interrupting device. This is software polling.
An interrupt system that uses extra hardware to identify an interrupting device is known as a vectored interrupt system. Vectored interrupts contain enough address information within the interrupt to identify the device that has interrupted. As a consequence the CPU can jump immediately to the correct ISR.
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