本代码按照DOD5220.22M标准来擦掉需要删除的机密数据，即首先将要删除的文件内容全部写为 0 ，再被写为 1 ，如此重复3次，接着被写上一个随机值；再加上一个DOD标准中未说明的步骤，即在删除文件之前，先将文件长度置为0，这使恢复机密文件的希望更为渺茫。-DOD5220.22M according to the code standards to wipe the need to remove confidential data, First, will be deleted all the content of the documents was made to 0, then wrote to a so repeat three times, are then written on a random value; coupled with a DoD standard unspecified steps to delete the file that is before given the length of documents home to 0, which makes restoring hope confidential documents of the more elusive.