Unity - How to write console

Use the Debug class to write to the Unity console.

E.g.:

if (Input.touchCount > 0 && Input.GetTouch (0).phase == TouchPhase.Began) {
    float x = Input.GetTouch(0).position.x;
    float y = Input.GetTouch(0).position.y;
    Debug.Log("x " + x + " - y " + y);
}