dontcare

Dontcare is a term used to indicate indifference or an unspecified value in a context where the exact value is not important to the outcome. In everyday language, "don't care" expresses a lack of preference or concern.

In digital logic and computer engineering, a don't-care condition refers to an input combination for which the function's output is not specified or does not affect the desired result. Such conditions may occur because the combination never occurs in real operation, or because any value (0 or 1) yields an acceptable outcome. Don't-care conditions are often indicated in truth tables with a dash or an X and are used to simplify Boolean expressions, especially in Karnaugh maps. During minimization, the designer can assign 0 or 1 to don't-care entries to produce a circuit with fewer gates.

Don't-care conditions are distinct from known zeros or ones in the function's defined outputs and from undefined values. They must be used within the rules of the design process; misinterpretation can lead to incorrect hardware.

Beyond electronics, the term appears in testing and data processing to denote values whose exact value is irrelevant to the outcome, allowing focus on meaningful results. In practice, careful specification distinguishes true inputs from don't-care possibilities to avoid ambiguity.