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Windows API: ANSI and Wide-Character Strings -- Is it UTF8 or ASCII? UTF-16 or UCS-2 LE?

Asked 2011-01-04T09:45:46.633
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I'm not quite pro with encodings, but here's what I think I know (though it may be wrong):

  1. ASCII is a 7-bit, fixed-length encoding, with the characters you can find in ASCII charts.
  2. UTF8 is an 8-bit, variable-length encoding. All characters can be written in UTF8.
  3. UCS-2 LE/BE are fixed-length, 16-bit encodings that support most common characters.
  4. UTF-16 is a 16-bit, variable-length encoding. All characters can be written in UTF16.

Are those above all correct?

Now, for the questions:

  1. Do the Windows "A" functions (like SetWindowTextA) take in ASCII strings? Or "multi-byte strings" (more questions on this below)?
  2. Do the Windows "W" functions take in UTF-16 strings or UCS-2 strings? I thought they take in UCS-2, but the names confuse me.
  3. In WideCharToMultiByte, Microsoft uses the word "wide-character string" to mean UTF-16. In that context, then what is considered a "multi-byte string"? UTF-8?
  4. Is LPWSTR a "wide-character string"? I would say it is, but then, wouldn't that mean it's UTF-16? And wouldn't that mean that it could be used to display, say, 4-byte characters? If not, then... is displaying 4-byte characters impossible? (Windows doesn't seem to have APIs for those.)
  5. Is the functionality of WideCharToMultiByte a superset of that of wcstombs, and do they both work on the same type of string? Or does one, say, work on UTF-16 while the other works on UCS-2?
  6. Are file paths in UTF-16 or UCS-2? I know Windows treats it as an "opaque array of characters" from Microsoft's documentation, but per the C standard for functions like fwprintf, is there any standardized encoding?
  7. What is "ANSI" encoding? Is that even a correct term? And how does it relate to ASCII?
  8. (I had more
winapi unicode ascii widechar multibyte-functions
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1 Answer

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  1. *A functions used the active ANSI codepage.

  2. *W function use UTF-16.

  3. Multi-byte refers to whatever is passed in the CodePage parameter. It is most commonly either the active ANSI codepage or UTF-8.

  4. LPWSTR is a UTF-16 string which may or may not be null-terminated (see MSDN)

  5. I don't know anything about wcstombs, I always use WideCharToMultiByte.

  6. File paths are in UTF-16. In fact all text is UTF-16 internally in Windows.

  7. For ANSI encoding you will need to read up on that in some detail. You could do worse than to start with Wikipedia and follow the links from there.

I hope that helps and that if I've got anything wrong, anyone who knows more please do edit this to correct any errors!

answered 2011-01-04T12:00:36.710

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