Which register stores the address of the instruction currently being executed?

Which register stores the address of the instruction currently being executed?

• A. Program Counter (PC)
• B. Memory Data Register (MDR)
• C. Memory Address Register (MAR)
• D. Instruction Register (IR)

Answer: (C)

In the fetch phase, the processor needs to read the next instruction from memory. The Memory Address Register stores the address in memory that will be accessed, so it holds the target address for the memory operation. The program counter typically supplies that address and is used to advance to the next instruction, but the actual register that carries the memory address being accessed at that moment is the MAR. Once memory responds, the fetched data (the instruction bits) are brought into the data path, usually into the Memory Data Register and then loaded into the Instruction Register for decoding. The Instruction Register, not the address, contains the actual instruction being executed, and the MDR holds the data being transferred, not the address.

In the fetch phase, the processor needs to read the next instruction from memory. The Memory Address Register stores the address in memory that will be accessed, so it holds the target address for the memory operation. The program counter typically supplies that address and is used to advance to the next instruction, but the actual register that carries the memory address being accessed at that moment is the MAR. Once memory responds, the fetched data (the instruction bits) are brought into the data path, usually into the Memory Data Register and then loaded into the Instruction Register for decoding. The Instruction Register, not the address, contains the actual instruction being executed, and the MDR holds the data being transferred, not the address.