In a cache, which field identifies the cache line containing the block?

In a cache, which field identifies the cache line containing the block?

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

Answer: (A)

Cache addressing relies on splitting the address into tag, index, and offset. The index points to a particular cache line (or set) where the block could be stored, so it directly identifies which line to inspect. Once the line is selected by the index, the tag stored with that line is compared to the address tag to verify we have the correct block, and the offset selects the exact byte inside the block. The valid bit simply indicates whether that line actually contains valid data. So the field that identifies which cache line to look at is the index field.

Cache addressing relies on splitting the address into tag, index, and offset. The index points to a particular cache line (or set) where the block could be stored, so it directly identifies which line to inspect. Once the line is selected by the index, the tag stored with that line is compared to the address tag to verify we have the correct block, and the offset selects the exact byte inside the block. The valid bit simply indicates whether that line actually contains valid data. So the field that identifies which cache line to look at is the index field.