The TCHAR data type is a Win32 character string that can be used to describe ANSI, double-byte character set (DBCS), or Unicode strings. For ANSI and DBCS platforms, TCHAR is defined as shown in the following Syntax section. For Unicode platforms, TCHAR is defined as synonymous with the WCHAR type.
MAPI clients can use the TCHAR data type to represent a string of either the WCHAR or the char type. Be sure to define the symbolic constant UNICODE, and limit the platform where necessary. MAPI interprets the platform information and internally translates TCHAR to the appropriate string. The MAPI property type PT_TSTRING works the same way as the TCHAR data type. When the platform supports Unicode, properties of type PT_TSTRING are assigned the type PT_UNICODE at compile time. When the platform does not support Unicode, these properties are assigned the type PT_STRING8.