例23：LCD1602显示

代码说明：

  字符型液晶显示模块是一种专门用于显示字母、数字、符号等点阵式LCD，目前常用16*1，16*2，20*2和40*2行等的模块。本程序为1602控制程序。(Character LCD module is a kind of lattice LCD which is used to display letters, numbers, symbols and so on. At present, 16*1, 16*2, 20*2 and 40*2 lines are commonly used. This procedure is the 1602 control procedure.)