69. Binary Subtractor

/*Write your code here*/
module sub4_2c(
    input  [3:0]a,
    input  [3:0]b,
    output [3:0]diff,
    output bout
);
    wire [4:0]result;
    assign result = {1'b0, a} + {1'b0, ~b} + 5'b00001;
    assign diff = result[3:0];
    assign bout = ~result[4];
endmodule