Memory Buffer Register (MBR): Contains a word of data to be written to memory or the word most recently read. Contents of MBR is directly connected to the data bus.It is also known as Memory Data Register(MDR).

Apart from these specific register, we may have some temporary registers which are not visible to the user. As such, there may be temporary buffering registers at the boundary to the ALU; these registers serve as input and output registers for the ALU and exchange data with the MBR and user visible registers.