Programmed I/O, interrupt-driven I/O and direct access memory (DMA) are three synchronisation methods to control data transfer between I/O devices and the CPU. Which one of the following statements is TRUE for interrupt-driven I/O?
1. The CPU keeps checking the status of the I/O device. When it is ready, the CPU transfer the data.
2. The I/O device informs the CPU that it is ready for data transfer.
3. Large blocks of data is transferred via a controller to relieve the CPU of some functions.
4. A lot of CPU time is wasted with the interrupt-driven method.