设计程序从D盘根目录的n.txt文件中的一个整型数据读出作为n，将2～n之间的素数计算出来存储到n.txt同文件夹的prime.txt文本文件中-Design process from the D root directory n.txt file data read-out as an integer n, the 2 ~ n calculated between the prime store n.txt same folder prime.txt text file