Multiplexer function clarity: Does a multiplexer (MUX) choose which output to send an input to, or does it choose which input is forwarded to a single output?

Introduction / Context:
Multiplexers and demultiplexers are duals but not identical. A multiplexer selects exactly one of many inputs and forwards it to a single output based on select lines. A demultiplexer takes a single input and routes it to one of many outputs. The stem incorrectly describes a demultiplexer as if it were a multiplexer. Clarifying this prevents common wiring errors in datapaths and I/O selection networks.

Given Data / Assumptions:

• MUX: many-to-one (N inputs, 1 output).
• DEMUX: one-to-many (1 input, N outputs).
• Select lines determine which path is active.

Concept / Approach:
A k-select-line MUX chooses one of 2^k inputs to appear at a single output. Conversely, a k-select-line DEMUX activates one of 2^k outputs to receive the single input. Hence the statement “chooses which output to send an input to” describes a DEMUX, not a MUX. Therefore, as a definition of a multiplexer, the statement is incorrect.

Step-by-Step Solution:

Verification / Alternative check:
Typical parts: 74HC157 (2:1 quad MUX) selects between inputs for a single output per channel. 74HC138 (3:8 decoder/DEMUX) routes one enable/input to one of eight outputs—distinct functions.

Why Other Options Are Wrong:
Limiting to 2:1 or invoking tri-state buses does not change the core definition. “True for demultiplexers” acknowledges the dual but confirms the statement is not correct for MUX.

Common Pitfalls:
Using the wrong symbol in schematics; confusing enable pins with select lines; forgetting that MUX outputs are singular per channel.

Final Answer:
Incorrect