&~ operation in C

commandline session

 switch (_NSIG_WORDS) {
        default:
                for (i = _NSIG_WORDS, ready = 0; --i >= 0 ; )
                        ready |= signal->sig[i] &~ blocked->sig[i];
                break;

        case 4: ready  = signal->sig[3] &~ blocked->sig[3];
                ready |= signal->sig[2] &~ blocked->sig[2];
                ready |= signal->sig[1] &~ blocked->sig[1];
                ready |= signal->sig[0] &~ blocked->sig[0];
                break;

        case 2: ready  = signal->sig[1] &~ blocked->sig[1];
                ready |= signal->sig[0] &~ blocked->sig[0];
                break;

        case 1: ready  = signal->sig[0] &~ blocked->sig[0];
        }

Related Note : Bitwise Logical Operators and Complex Conjugation Operators.
code source: Linux Kernel Related.
http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html