Nothing appears on arduino DUE screen

Hello all.

I am trying to run a very simple "Hello World" code, but nothing appears on my serial screen
Evetything looks fine, arduino is connected, the code is compiled, and succesfully verified. But nothing appears on screen. Here is my code, any ideas?

void setup() // run once, when the sketch starts
{
Serial.begin(9600); // set up Serial library at 9600 bps

}

void loop() // run over and over again
{
Serial.println("Hello world!"); // prints hello with ending line break
}

Anyone? please....

Still nothing, in all the computers i've tried!

Any help? Please!

Did you connect using programming or native port?

native port. When i use programming port i get the following error:

SAM-BA operation failed

If you use the native port you muste use "SerialUSB" for communication with the computer.

Patouf:
If you use the native port you muste use "SerialUSB" for communication with the computer.

Exactly. Thats why I asked.

So, what should i do? Can you please help me a litle more on that?
I had never used the Due board before and i am really annoyed at the moment...

I used the Programming Port and it finally works! But i think prefer the Serial one, just because the arduino box is only designed for this one!

When using the native port, do it like this:

void setup()                    // run once, when the sketch starts
{
  SerialUSB.begin(9600);           // set up Serial library at 9600 bps
}

void loop()                       // run over and over again
{
 SerialUSB.println("Hello world!");        // prints hello with ending line break                             
}