在用户程序中可使用文件系统提供的一整套文件操作（文件类系统调用），这类操作一般包括“打开文件”、“关闭文件”、“读文件”、“写文件”和“撤消文件”等。本实习模拟文件操作的实现，通过实习了解各文件操作的作用。-In the user program can use the file system provides a set of file operations (file type system calls), such operations generally include " open file" , " Close file" , " reading file" , " write file"　and " Undo Files"　and so on. The internship simulate file operations to achieve, through practical understanding of the role of the various file operations.