In computer architecture, which addressing mode provides access to an operand at an address defined relative to the start of the data structure in which it resides?

Introduction / Context:
Addressing modes specify how the CPU computes the effective address of an operand. They are essential for working with arrays, records/structs, and tables. Correctly identifying an addressing mode helps in understanding how compilers layout data and how instructions fetch operands at runtime.

Given Data / Assumptions:

• The operand's location is relative to the beginning of a data structure.
• The interest is in a mode that naturally supports offsets within a structure or array.
• Terminology aligns with standard ISA descriptions (index, indirect, etc.).

Concept / Approach:

Index addressing uses a base address (often the start of a data structure) plus an index or offset to calculate the effective address: EA = base + index. This maps directly onto array indexing and field offsets. Indirect addressing dereferences a pointer but does not by itself add a structure-relative offset unless combined with indexing.

Step-by-Step Solution:

Verification / Alternative check:

Common ISAs (x86 base+index+disp, ARM base+offset) implement index addressing for arrays and struct fields, reinforcing the choice.

Why Other Options Are Wrong:

• ascending/sorting: algorithmic terms, not addressing modes.
• indirect: dereferences a pointer; alone it does not encode structure-relative indexing.
• None of the above: incorrect because index addressing matches exactly.

Common Pitfalls:

• Confusing indirect with indexed-indirect modes; the presence of an offset is key.

Final Answer:

index.