unknown construction

While I was digging up some sources(mpd daemon for FreeBSD to be more precise) i had found this:

u_char want_protocomp:1; /* I want protocol compression */
u_char want_acfcomp:1; /* I want a&c field compression */
u_char want_multilink:1; /* I accept multi-link */

I know the " ? : " operator
and "::" operator but not just single conon mark.

Does anybody know what can this mean?