Strange behaviour of visual studio 2008 with escape sequence

Regarding C programming language, the descriptions of escape sequence does not resolve the output of following line in visual studio 2008.

char * str = "??/abc"; printf( "%s", str );

it prints only "bc". Checking the memory pointed by str, we can find that "??/a" is working as "\a"

Searching on google we can't find anything related to "??/" being treated as backslash.