将键盘上输入的字符在屏幕上显示出来。键盘和显示器屏幕是标准输入输出设备，数据输入的起点为键盘，数据输出的终点是屏幕，输出的数据可以在屏幕上显示出来。-The characters entered on the keyboard displayed on the screen. A keyboard and a display screen is the standard input and output devices, the keyboard data input start point, the end of the screen output data, output data can be displayed on the screen.