// Different ways to write decoders 
//in always blocks
module decoder(W, Y, En);
input [1:0] W;
input En;
output [3:0] Y;
reg [3:0] Y;

always @(W or En)
begin
	// concatenation {En, W}
	case({En, W})
		3'b100:begin Y = 4'b0001;  end
		3'b101: Y = 4'b0010;
		3'b110: Y = 4'b0100;
		3'b111: Y = 4'b1000;
		default: Y= 4'b0000;
	endcase									 
end

/*----- What do you think about this? --*/
/* Will the following code work correctly as a combinational decoder
circuit? If yes, why? If not, why not? Find out! */
/*-------
always@(En, W)
begin
	if(En == 0) Y=4'b0000;
	else
	case(W)
		2'b00: Y = 4'b0001;
		2'b01: Y = 4'b0010;
		2'b10: Y = 4'b0100;
		2'b11: Y = 4'b1000;
	endcase
end
-------*/

/* And what about the following code, see carefully... */
/*---------
always@(En, W)
begin
	if(En == 0) begin
		Y=4'b0000;
	end

	case(W)
		2'b00: Y = 4'b0001;
		2'b01: Y = 4'b0010;
		2'b10: Y = 4'b0100;
		2'b11: Y = 4'b1000;
	endcase
end
------------*/

endmodule