MSI fundamentals — identify the component: A digital device has several input lines, exactly one of which is asserted (active) at any given time. Depending on which single input is active, the device produces an N-bit binary code at its outputs that represents that input’s numeric index. What is this device called?

Introduction / Context:
This question targets medium-scale integration (MSI) building blocks used in digital systems. Many textbooks distinguish between devices that select among inputs (multiplexers), distribute one input to many outputs (demultiplexers), translate between codes (encoders/decoders), and compare binary words (comparators). Here, the behavior described is one-hot to binary coding, which is foundational in keyboards, interrupt systems, and priority logic.

Given Data / Assumptions:

• There are multiple input lines; at most one is asserted at a time.
• The output is an N-bit binary word representing the index (or identity) of the active input.
• We ignore tie cases (simultaneous inputs) unless a priority version is implied.
• Outputs are stable for valid, single-active input conditions.

Concept / Approach:
An encoder converts a one-hot (or one-of-2^N) input pattern into an N-bit binary code. A classic example is an octal-to-binary encoder that maps eight inputs to a 3-bit output. A decoder performs the inverse mapping: an N-bit code word selects one of 2^N outputs. A demultiplexer routes one input line to one of many outputs under control of select lines, not to a binary code.

Step-by-Step Solution:
Identify mapping direction: many inputs (one active) → compact N-bit code.Match with standard MSI definitions: this is the function of an encoder.Exclude other categories: a decoder is code to one-hot; a demultiplexer is data distribution; a code converter may change code formats but not necessarily one-hot to binary.Therefore, the correct classification is “encoder.”

Verification / Alternative check:
Part families such as 74148 (8-to-3 priority encoder) and 74HC147 demonstrate exactly this behavior. Their truth tables show a single asserted input producing a binary code on the outputs.

Why Other Options Are Wrong:
Code converter is too generic and does not imply one-hot to binary with a single active input. Demultiplexer distributes a single input to one of many outputs. Decoder is the inverse of the described behavior.

Common Pitfalls:
Confusing encoder/decoder directions; overlooking priority encoders where multiple actives are resolved by priority, yet the device is still an encoder.

Final Answer:
encoder