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 an