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MSDN Forums >> Visual Studio Developer Center >> TCHAR vs _TCHAR
TCHAR and _TCHAR are identical,although since TCHAR doesn’t have a
leading underscore,Microsoft aren’t allowed to reserved it as a
keyword (imagine if you had a variable called TCHAR. Think what would
happen). Hence TCHAR will not be #defined when Language Extensions are
disabled (/Za).TCHAR is defined in winnt.h (which you’ll get when you #include ),and also tchar.h under /Ze. _TCHAR is available only in tchar.h (which also #defines _TSCHAR and _TUCHAR). Those are unsigned/signed variants of the normal TCHAR data type.
