module ALU_pv(input [3:0] aluin_a, opcode, input Cin, output reg [3:0] alu_out, output reg cout, of);
   wire [3:0] aluin_b;
   assign aluin_b = 4'b 0011;
   ALU alu(aluin_a, aluin_b, opcode, Cin, alu_out, Cout, OF);
endmodule