ALU control concept: The selector (control) inputs to an arithmetic-logic unit determine what aspect of its operation?

Introduction / Context:
An arithmetic-logic unit (ALU) is the computational heart of a processor or digital datapath. Control or selector lines command the ALU to perform specific operations on its inputs, enabling instruction execution and micro-operations.

Given Data / Assumptions:

• We consider a generic multi-function ALU with control lines (e.g., S₀…Sₙ).
• Inputs A and B are operand words; flags may reflect results.

Concept / Approach:
ALU selector inputs choose among available functions: addition, subtraction (via two’s complement), increment, decrement, logical AND/OR/XOR/NOT, shifts/rotates (if integrated), etc. They do not select the chip itself, the data source, or the system clock rate; those are managed by other subsystems (decoder, multiplexers, clock generator).

Step-by-Step Solution:

Verification / Alternative check:
Examine classic ALUs (e.g., 74181). Control bits determine whether the unit performs arithmetic vs. logic operations and which specific function, confirming the principle.

Why Other Options Are Wrong:

• selection of the IC: Handled by chip-select, not ALU function selectors.
• data word selection: Controlled by multiplexers and register enables.
• clock frequency: Provided by the system clock, independent of ALU function codes.

Common Pitfalls:
Confusing ALU function control with instruction decode or bus selection signals; remember the ALU only transforms input data according to these selector codes.

Final Answer:
arithmetic or logic function