Learn: Data vs Address in Registers

Welcome!You've already explored how registers like MAR and MDR work in the CPU. Now, let's build on that by learning how to tell apart data and addresses in registers.

What are Data and Addresses?Registers in the CPU store information needed for processing. This information can be data (the actual value being processed) or an address (location in memory where data is stored).Understanding the difference is essential for knowing how instructions move through the fetch–execute cycle.

Memory Address Register (MAR)The MAR stores the address of the memory location the CPU wants to access. This could be to fetch data or an instruction.For example, if the CPU needs data stored at memory location 5, the MAR will hold the value 5.

Memory Data Register (MDR)The MDR holds the data fetched from memory or data that is to be written to memory. It works closely with the MAR to ensure the right data is accessed.For instance, if the CPU fetches the value 42 from memory location 5, the MAR holds 5 (the address) while the MDR holds 42 (the data).

How Data and Addresses Work TogetherDuring the fetch–execute cycle, the CPU uses the MAR and MDR together. The MAR identifies where to look in memory, and the MDR retrieves or stores the data at that location.This ensures instructions and data move efficiently through the CPU.

Review Time!Great work! You've learned about how the CPU distinguishes between data and addresses in registers. Let's test your understanding!