统计一个文件中任意单词的个数。在文件中的指定位置添加字符串，并保存到文件中。在文件中的批定位置删除指定长度字符串，并保存文件。读文件中指定行的字符串，并显示。计算读文件的速度。计算写文个的速度。-Statistics on a file in any number of words. In the document to add the string of the specified location and save it to file. Approved in the document will be the location of the deletion of the designated length of string, and save the file. Reading a document specified in the string line, and displayed. Calculated the speed of reading a document. Write a calculation of the speed of text.