说明：  C语言中产生随机数的代码，编写成了子程序的形式，可以在需要使用的源程序中调用。真正实现时间函数，每次调用随机数均不相同，每次运行随机数也不相同。产生的随机数大于0，小于等于1
(C language generated random number code, prepared become subroutine in the form of the need to use the source code call. To achieve real time functions, random number for each call is different, each running from the same random number. The random number greater than 0 and smaller than or equal to 1)