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

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

• A. Program Counter
• B. Memory Address Register (MAR)
• C. Accumulator
• D. Data Bus

Answer: (B)

The key idea is how memory access is controlled during instruction fetch. The Memory Address Register holds the address of the memory location that is being accessed by the current operation. When the CPU is fetching an instruction, the address of that instruction is placed into the MAR so memory can be read at that location, and the instruction is then loaded into the Instruction Register. After the fetch, the Program Counter is updated to point to the next instruction, so it stores the address of the upcoming instruction rather than the one currently being executed. The Accumulator and Data Bus are involved with processing and transferring data, not keeping memory addresses for the current instruction. Therefore, the register that holds the address of the instruction currently being accessed is the Memory Address Register.

The key idea is how memory access is controlled during instruction fetch. The Memory Address Register holds the address of the memory location that is being accessed by the current operation. When the CPU is fetching an instruction, the address of that instruction is placed into the MAR so memory can be read at that location, and the instruction is then loaded into the Instruction Register. After the fetch, the Program Counter is updated to point to the next instruction, so it stores the address of the upcoming instruction rather than the one currently being executed. The Accumulator and Data Bus are involved with processing and transferring data, not keeping memory addresses for the current instruction. Therefore, the register that holds the address of the instruction currently being accessed is the Memory Address Register.