Problem Statement
What is Direct Memory Access (DMA) in the context of I/O systems?
Explanation
DMA allows a hardware controller (the DMA engine) to move data between memory and a device without continuous CPU intervention. This frees the CPU to perform other tasks while large blocks of I/O are transferred. An OS using DMA must coordinate memory buffers, interrupt service routines and bus arbitration. Understanding DMA is often asked in system-level OS interviews because it touches hardware-software boundary.
