Which unit holds the address of where data or instructions will be fetched from or stored?

• A. Memory Data Register
• B. Program Counter
• C. Cache
• D. Memory Address Register

Answer: (D)

The Memory Address Register is what holds the address used for memory read or write operations. When the CPU needs to fetch data or an instruction, that location’s address is loaded into the MAR, which then places it on the address bus to the memory unit. The actual data being transferred moves through the Memory Data Register, not the MAR. The Program Counter does hold the address of the next instruction to fetch, but it’s not the general address holder for every memory access. The cache is a fast storage that speeds up repeated accesses, not the dedicated place to store the target address. So, the MAR is the unit that specifies where in memory the data or instruction should be accessed.