/Zc:trigraphs (Trigraphs Substitution)
When /Zc:trigraphs is specified, the compiler replaces a trigraph character sequence by using a corresponding punctuation character. To turn off trigraph substitution, specify /Zc:trigraphs-. By default, /Zc:trigraphs is off.
A trigraph consists of two consecutive question marks ("??") followed by a unique third character. For example, the compiler replaces the "??=" trigraph by using the '#' character. Use trigraphs in C source files that use a character set that does not contain convenient graphic representations for some punctuation characters.
For a list of C/C++ trigraphs, and an example that shows how to use trigraphs, see Trigraphs.