COMPUTER SCIENCE AND ENGINEERING
COMPUTER ARCHITECTURE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Once the current instruction has been fetched
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Once the current instruction has been decoded
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Once the current instruction has been executed
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It doesn’t point to the next instruction
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Detailed explanation-1: -During the fetch stage, the address stored in the PC is copied into the memory address register (MAR) and then the PC is incremented in order to “point” to the memory address of the next instruction to be executed.
Detailed explanation-2: -Usually, the PC is incremented after fetching an instruction, and holds the memory address of ("points to") the next instruction that would be executed. Processors usually fetch instructions sequentially from memory, but control transfer instructions change the sequence by placing a new value in the PC.
Detailed explanation-3: -The program counter now holds the address of the next instruction to be fetched. The processor sends a signal along the address bus to the memory address held in the MAR. The instruction/data held in that memory address is sent along the data bus to the MBR/MDR .
Detailed explanation-4: -Data Memory The most common way in which a program runs is from one instruction to the next in the memory. The program counter is automatically incremented by one after each instruction so that the next instruction can be loaded.
Detailed explanation-5: -The CPU uses the PC to keep track of where it is in the program it is executing. The PC simply stores the memory address of the next instruction that the CPU should execute. At the beginning of each fetch-and-execute cycle, the CPU checks the PC to see which instruction it should fetch.