Widestring

Widestring is a data type used to store Unicode text as a sequence of 16-bit code units, typically UTF-16. It is most closely associated with Windows environments and is widely used for interoperation with COM (Component Object Model) and OLE automation, where BSTR strings are common. Widestrings appear in legacy code and in languages that emphasize COM compatibility.

In practice, a widestring stores 16-bit Unicode characters and can accommodate embedded nulls, since its length is explicitly tracked rather than determined by a terminating character. Memory management for widestrings is designed to align with COM/BSTR conventions in many environments, meaning they are often reference-counted and freed when no longer in use. This makes widestrings suitable for calling Windows APIs and COM methods that expect BSTR-like data.

Widestrings are distinct from UnicodeString in modern Delphi and related languages. WideString is the older, COM-friendly type intended for interop, while UnicodeString is the newer, more general-purpose Unicode type used for normal string handling within the language runtime. For new code, UnicodeString is usually preferred unless there is a specific need to interoperate with COM or BSTR-based APIs, in which case widestring remains relevant. In C++ and other languages on Windows, wide-character types based on UTF-16 serve a similar role, though exact semantics can vary by language and runtime.

Overall, widestring continues to appear in legacy code and interop scenarios with Windows COM, while modern native string types provide broader functionality and better integration with contemporary language features. See also BSTR, UTF-16, wchar_t, and UnicodeString.