The tag field in a cache address identifies which memory block is stored in a cache line.

• A. Tag Field
• B. Index Field
• C. Offset Field
• D. Block Field

Answer: (A)

In cache addressing, an address is split into tag, index, and offset. The index selects which cache line to check, and the offset picks the exact data inside the line’s block. The tag stores the upper bits of the memory block’s address so you can verify that the block currently in that line matches the address you’re asking for. When you access memory, you compare the tag stored with the address’s tag portion. If they match, the line holds the desired block, which is a hit; if not, it’s a miss and the line will be updated with the correct block and its tag. Because the tag provides the actual block identity within that line, it identifies which memory block is stored there. The index and offset do not identify the block by themselves—the index points to the line, and the offset locates data within the block. There isn’t a separate block field in this standard scheme.