What is m wcostream?

std::wcostream is a class in the C++ standard library that represents an output stream that writes wide-character data to a file or device. It is similar to std::wofstream, but with the addition of support for localized formatting and output encoding conversion. The wcostream class is a part of the <iostream> header in C++.

std::wcostream can be constructed in a similar way to other C++ output streams, such as std::ofstream. It exposes methods for writing wide-character data to the stream, such as put, write, and operator<<. It also supports the insertion operator (<<) with manipulators like std::setw, std::setfill, and std::setprecision for formatting.

The character encoding used by the wcostream can be specified by setting a locale for the stream. The stream will then perform encoding and decoding of characters to and from the specified encoding as needed. This allows for seamless output of multi-byte characters and strings to a variety of output devices and files that may not use the same encoding as the program.

Overall, std::wcostream provides a convenient way to output wide-character data to files and devices, with support for localization and encoding conversion. It is a useful tool for text-based programs that need to work with non-ASCII character sets and multi-byte encodings.