51常用子程序。包括：液晶，ad，da，音乐播放，打印，电机，查表，通讯等等好多好东西。-51 commonly used subroutines. Include: LCD, ad, da, music players, printing, electrical, inventory, communications and so on a lot of good things.

一些关于51单片机的常用应用例程，包括通讯，LCD显示(Some common applications on the 51 microcontroller routines, including communications, LCD display)