Digital Logic Fundamentals — Decoder Definition and Role In digital electronics, a circuit that recognizes a specific input code or set of input signals and asserts a corresponding output line (or pattern) is called a:

Introduction / Context:
A decoder is a fundamental combinational logic block used to translate coded inputs into a set of mutually exclusive outputs. Whenever a system needs to identify which code, address, or state is present and activate the corresponding line, a decoder performs this selection. Decoders appear in memory addressing, instruction decoding, seven-segment driving (via BCD-to-7-segment ICs), and chip-select logic.

Given Data / Assumptions:

• The circuit observes a set of input signals (for example, n-bit binary or BCD).
• For each valid input code, a well-defined output line or pattern is produced (often one-hot).
• The question asks for the general name of such a circuit.

Concept / Approach:
In a decoder, inputs represent a code and outputs represent decoded lines. An n-to-2^n decoder activates exactly one of 2^n outputs for each n-bit input combination (ignoring enable and don’t-care cases). In contrast, an encoder converts many input lines into a coded (typically binary) output. A display driver may include decoding but is a more specific functional block, and a “BCD matrix” is not a standard generic name in this context.

Step-by-Step Solution:
Identify behavior: recognize input code → assert corresponding output line.Map to standard block: this is the canonical definition of a decoder.Exclude alternatives: encoder performs the inverse mapping; display driver is application-specific; “BCD matrix” is nonstandard.Therefore, the circuit is a decoder.

Verification / Alternative check:
Typical parts such as 74xx138 (3-to-8 decoder) or 74xx154 (4-to-16 decoder) behave exactly as described: for each binary input, one unique output goes active when enabled.

Why Other Options Are Wrong:

• display driver: Usually includes current limiting, multiplexing, and sometimes decoding, but is not the generic name for the decoding function.
• encoder: Converts many inputs to fewer coded outputs (opposite direction).
• BCD matrix: Not a standard term for this fundamental function.

Common Pitfalls:
Confusing “decoder” with “driver/encoder,” or assuming any display-related IC is necessarily a decoder. Always check whether the block maps code→line (decoder) or line→code (encoder).

Final Answer:
decoder