how to reference key down in unity code example

Example 1: unity key detection

if (Input.GetKeyDown(KeyCode.Space))
        {
            print("space key was pressed");
        }

Example 2: unity key detection

void Update()
    {
        if (Input.GetKeyDown("space"))
        {
            print("space key was pressed");
        }
    }

Example 3: unity getkey keycode

Input.GetKey(KeyCode.Space))