`define add 3'd0
`define minus 3'd1
`define band 3'd2
`define bor 3'd3
`define bnot 3'd4
module alu(out,opcode,a,b);
output[7:0] out;
reg[7:0] out;
input[2:0] opcode;
input[7:0] a,b;

always@(opcode or a or b)
begin
case(opcode)
`add: 	out = a+b;
`minus: out = a-b;
`band: 	out = a&b;
`bor: 	out = a|b;
`bnot: 	out=~a;
default: out=8'hx;
endcase
end
endmodule