What defines a semantic error in programming?

A semantic error in programming refers to a situation where the code is syntactically correct—meaning it adheres to the rules of the programming language—but does not produce the intended results or behavior as envisioned by the programmer. This can arise from misunderstanding the logic or the sequence of operations in the code, leading to outcomes that contradict what was intended.

For illustrative purposes, consider a scenario where a programmer might correctly write a function to compute the area of a rectangle using valid syntax, but inadvertently calculates the perimeter instead. Although the code runs without errors and adheres to the required syntax, it does not fulfill the programmer's intent to calculate the area, thus exemplifying a semantic error.

The other options highlight different types of issues in programming. For example, if code cannot be executed at all, that typically indicates a syntax error. Likewise, language compatibility issues pertain to problems where code written in one programming language does not operate correctly in another, rather than reflecting a misunderstanding of the code’s meaning. Finally, logical errors may result from semantic issues, but they specifically refer to incorrect logical constructs rather than broader misalignments between the code's execution and the programmer's intentions.