How do I define a constant as being a bit string IE a string of binary values rather than a string of characters.

for example I can write
#define test "Blah Blah Blah"
and that works fine,or I can write
#define test 'xFF'
and that works as well,but I want to write
#define test 'xFF''xDD''x38' but thats clearly not the way to do it.
Hellup!!!!