在许多应用程序领域中，都需要控制小数点后的小数位，但是浮点数对此不能提供直接的支持。怎样对程序中的浮点数据进行"整齐"地格式化呢？在此我们有一个迂回的方法，先把它们转换为字符串，格式化后以文本形式显示出来。 -In many applications areas, both need to control the decimal places after the decimal point, but the floating-point numbers which can not provide direct support. How the program in the floating-point data, " neat"　to format it? Here we have a roundabout way, first they are converted to a string, formatted as text displayed.