Since a square wave has infinite harmonics, and digital systems can only reproduce up to half the sample rate (the Nyquist frequency), no digital system can accurately reproduce a perfect square wave. For example, at a 48kHz sample rate, band limiting filters would remove frequencies above 24kHz. The rise and fall of the waveform would not be as steep or it could be slightly rounded.Analog recorders have their own limitations, which are not limited by sample rate but by frequency response of the electronics and the tape.