VLSI: BCD to Excess 3 and Excess 3 to BCD Dataflow Modelling

module bcd_ex3_Dataflow(
    input a,
    input b,
    input c,
    input d,
    output w,
    output x,
    output y,
    output z
    );

assign w = (a | (b & c) | (b & d));
assign x = (((~b) & c) | ((~b) & d) | (b & (~c) & (~d)));
assign y = ((c & d) | ((~c) & (~d)));
assign z = ~d;

endmodule

Excess 3 to BCD:

module ex3_to_bcd(

    input w,

    input x,

    input y,

    input z,

    output a,

    output b,

    output c,

    output d

    );

assign a = ((w & x) | (w & y & z));

assign b = (((~x) & (~y)) | ((~x) & (~z)) | (x & y & z));

assign c = (((~y) & z) | (y & (~z)));

assign d = ~z;

endmodule