We have to design a second order Butterworth filter having a sampling frequency of 20 kHz and -3db cut of frequency at 2 kHz in visual C. Only low frequency signals can pass through this filter and the signals having the frequency higher than frequency called cut off frequency get attenuated by this filter. we will use bilinear transform which is one of the most efficient way of converting a analogue filter to digital filter, we will convert the given transfer function from Laplace transform to z-transform and then we will realize poles and zeroes in the z-domain. And their corresponding frequency response.-We have to design a second order Butterworth filter having a sampling frequency of 20 kHz and-3db cut of frequency at 2 kHz in visual C.　Only low frequency signals can pass through this filter and the signals having the frequency higher than frequency called cut off frequency get attenuated by this filter. we will　use　bilinear　transform　which is one of　the most　efficient way of　converting a　analogue filter　to digital filter, we　will convert　the given transfer function　 from Laplace transform to z-transform and　then we　will　realize　poles　and zeroes in the　z-domain.　And their corresponding frequency response.