VHDL base types — identify the item that is not a valid standard type In common VHDL practice with IEEE libraries, which of the following is not a recognized standard data type name?

Introduction / Context:
VHDL type correctness is critical for synthesizable code and clean simulations. IEEE packages (such as std_logic_1164) define widely used resolved types and arrays. Knowing the exact type names avoids compilation errors and unintended implicit conversions.

Given Data / Assumptions:

• We refer to standard types defined in the IEEE library and the language core.
• Case is not significant in VHDL, but exact identifiers matter.
• Array type names follow specific conventions.

Concept / Approach:
Core types include BIT and BIT_VECTOR. With IEEE std_logic_1164, the resolved scalar is STD_LOGIC and the array is STD_LOGIC_VECTOR. There is no standard type named STD_VECTOR; using it would produce a compile error unless a user-defined type shadows that name.

Step-by-Step Solution:
List known scalar types: BIT, STD_LOGIC.List matching vector types: BIT_VECTOR, STD_LOGIC_VECTOR.Compare options; detect that STD_VECTOR is not one of the standard names.

Verification / Alternative check:
Examine IEEE package declarations or compile a small VHDL snippet declaring signals of each listed type to see which names pass type checking.

Why Other Options Are Wrong:
BIT, BIT_VECTOR, and STD_LOGIC are legitimate standard types and compile under typical toolchains with the right library use clauses.

Common Pitfalls:
Mixing BIT/STD_LOGIC without proper conversions; forgetting to include IEEE std_logic_1164 leads to unknown identifiers for STD_LOGIC-based types.

Final Answer:
STD_VECTOR