In a computer system, which of the following two registers are used by

In a computer system, which of the following two registers are used by the CPU to transfer the data between processor and memory ?

[amp_mcq option1=”MDR and IR” option2=”PC and IR” option3=”MAR and MDR” option4=”IR and MAR” correct=”option3″]

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UPSC CISF-AC-EXE – 2021

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The correct answer is C) MAR and MDR.

When the CPU needs to access memory (either to read data/instruction or write data), it uses two primary registers for the transfer:
1. Memory Address Register (MAR): Stores the address of the memory location the CPU wants to access.
2. Memory Data Register (MDR) or Memory Buffer Register (MBR): Temporarily stores the data being read from or written to the memory location specified by the MAR. Data flows between the MDR and the data bus, and between the data bus and memory.

The Instruction Register (IR) holds the current instruction being executed. The Program Counter (PC) holds the address of the *next* instruction. While PC is used to fetch the next instruction (by placing its value in MAR), IR and PC are not the registers directly involved in the data *transfer* between the processor and memory in a general sense; that role is specific to MAR and MDR.

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