A digital pin will most likely output a signal using a zero-order hold, which is the simplest type of reconstruction filter. A zero-order hold is just one poss

A digital pin will most likely output a signal using a zero-order hold, which is the simplest type of reconstruction filter. A zero-order hold is just one possible way of turning a digital signal into an analog one which you can then measure with your oscilloscope. But the output of the zero-order hold is not the digital signal, because the digital signal is only defined at discrete sample points.