一个文件在磁盘上占用的空间与该文件的实际长度是两个不同的概念。文件的实际长度固定不变．但在磁盘上占用的空间大小则因所用机型、DOS版本号及介质环境的不同而不同，了解文件在磁盘中占用空间的分配，对于管理开发应用软件，有效地利用资源具有重要意义。我们知道，DOS在 The space a file occupies on disk and the actual length of the file are two different concepts. The actual length of the file is fixed. However, the amount of space occupied on the disk depends on the model used, the version number of the DOS and the environment of the medium. It is of great significance to understand the allocation of the space occupied by the files in the disk for the purpose of managing and developing the application software and effectively utilizing the resources. We know, DOS is here