A Level Computer Science OCR Practice Exam 2025 - Free Practice Questions and Study Guide

The Memory Address Register (MAR) is an essential component of the CPU's architecture, particularly in its interaction with memory. Its primary function is to store the address of the memory location that is currently being accessed or is in use. When the CPU needs to read data from or write data to memory, it places the relevant memory address into the MAR. This address is then used by other components of the memory hierarchy to locate the specific data or instruction that the CPU requires.

By storing the address of the memory location currently in use, the MAR plays a crucial role in ensuring that the CPU can efficiently access the correct data without confusion. This means that the MAR acts as a reference point, directing memory operations and facilitating data transfer between the CPU and memory.

Other options refer to functions related to different registers or components within the CPU. For example, the storage of the next instruction to be executed is typically handled by the Program Counter (PC), while data currently being processed would be managed within the CPU's registers or specifically the Arithmetic Logic Unit (ALU). Similarly, data that is temporarily held before being written to memory would be managed by a buffer or similar structure. Understanding the specific roles of these elements helps clarify why storing the address of the currently accessed memory