Difference between subroutine and interrupt IO?

Subroutine I/O involves the CPU executing a series of instructions to perform input/output operations, where the CPU is actively involved in managing the data transfer. In contrast, interrupt I/O allows the CPU to continue executing other tasks while peripheral devices signal the CPU when they are ready for data transfer, thereby improving efficiency and responsiveness. Interrupts can preempt the current execution flow, allowing for asynchronous handling of I/O operations, while subroutines require the CPU to be dedicated to the I/O task until it completes.