<Dt> Memory address register (MAR) </Dt> <Dd> Holds the address of a block of memory for reading from or writing to . </Dd> <Dt> Memory data register (MDR) </Dt> <Dd> A two - way register that holds data fetched from memory (and ready for the CPU to process) or data waiting to be stored in memory . (This is also known as the memory buffer register (MBR).) </Dd>

Instruction execution life cycle aid of a diagram