9. XOR Gate Using Basic Gates

// ============================================================
// Basic Gates (given)
// ============================================================
module and_gate(input a, b, output y);
    assign y = a & b;
endmodule

module or_gate(input a, b, output y);
    assign y = a | b;

endmodule

module not_gate(input a, output y);
    assign y = ~a;

endmodule

// ============================================================
// XOR Gate
// ============================================================
module xor_gate (
    input  a, b,
    output y
);
wire w1, w2;
wire p, q;

not_gate m1 (.a(b), .y(p));
not_gate m2 (.a(a), .y(q));
and_gate m3 (.a(a), .b(p), .y(w1));
and_gate m4 (.a(q), .b(b), .y(w2));
or_gate  m5 (.a(w1), .b(w2), .y(y));

endmodule