The IsDBCSLeadByte function determines whether a character is a lead byte ¾ that is, the first byte of a character in a double-byte character set (DBCS).
BOOL IsDBCSLeadByte(
| BYTE TestChar | // character to test | 
| ); | 
If the character is a lead byte, the return value is nonzero.
If the character is not a lead byte, the return value is zero. To get extended error information, call GetLastError.
Lead bytes are unique to double-byte character sets. A lead byte introduces a double-byte character. Lead bytes occupy a specific range of byte values. The IsDBCSLeadByte function uses the ANSI code page to check lead-byte ranges.