设计实验线路并编写程序，实现数字信号到模拟信号的转换，输入数字量由程序给出。产生方波和三角波和正弦波，并用示波器观察输出模拟信号的波形-Design the line and program, realize the digital signal to the analog signal conversion, enter the digital quantity are given by the program. Produce square wave and triangle wave and the sine wave, and observation of the analog signal output oscilloscope waveform