实现一个数字信号处理的仿真系统 。要求具有界面并实现以下功能： 1）能产生并选择各种数字信号（sin、方波、三角波）；2）用滤波器实现低通、高通、带通和带阻滤波；3）得到输出信号的频域特性和时间序列。

-The realization of a digital signal processing simulation system. Require an interface and realize the following functions: 1) to produce and select a variety of digital signal (sin, square wave, triangular wave)　2) low-pass filter, high pass, band pass and band-stop filter　3) to be output frequency domain characteristics of signals and time series.