Who “controls” a demultiplexer's outputs? In a standard digital demultiplexer (1-to-N), which signals directly determine which output line is driven?

Introduction / Context:
Demultiplexers route one input signal to one of several outputs. Knowing which signals govern the routing is crucial for timing analysis, HDL design, and system debugging.

Given Data / Assumptions:

• Device: 1-to-N DEMUX with select lines and a single data input.
• Enable input may also exist but is not central to the question.

Concept / Approach:
The select lines (also called address or control inputs) encode the index of the output line that will receive the data. Internally, logic gates decode the select pattern to enable exactly one output path; however, the external, user-controlled signals that choose the path are the select lines.

Step-by-Step Solution:

Verification / Alternative check:
Truth tables show that for each select code, exactly one output equals the data input (or its enabled form), confirming select-line control.

Why Other Options Are Wrong:

• Internal gates (AND/OR): Implementation detail, not user-controlled signals.
• Input data line: Provides the value to be routed, but does not choose the destination.

Common Pitfalls:

• Confusing data enables with address selection; enable controls whether routing occurs, not which line is chosen.

Final Answer:
input data select lines.