module decodeX4 (b0, b1, b2, b3, in0, in1);
            output b0, b1, b2, b3;
            input  in0, in1;             // select inputs
        
            not    N1 (t0, in0);         // invert inputs
            not    N2 (t1, in1);
                                 
            and    A1 (b0, t1, t0);      // decode inputs => outputs
            and    A2 (b1, t1, in0);
            and    A3 (b2, in1, t0);
            and    A4 (b3, in1, in0);
        endmodule