Which unit keeps track of the next instruction address in the sequence?

• A. Cache
• B. Program Counter
• C. MAR
• D. MDR

Answer: (B)

The unit that tracks the next instruction address is the program counter. It stores the address of the instruction the processor will fetch next from memory, and after each fetch it typically advances to the address of the following instruction. This makes it essential for the sequential flow of execution, and it can be updated to a target address during jumps or branches to implement control flow.

The other options don’t fit this role: a cache holds recently used data or instructions for faster access, a MAR (memory address register) stores the address to be accessed in memory during a memory operation, and a MDR (memory data register) holds the actual data being read from or written to memory.