设计并实现一个简单的行编辑系统。该系统提供5条编辑子命令：

open 文件名：将指定文件读入内存；

quit：将正在编辑的文件写回文件，退出编辑系统；

list n1 – n2：显示第n1到第n2行的内容；

del 行号，列号，字符数：从指定位置开始删除指定的字符数；

ins 行号，列号，字符串：在指定位置插入字符串。-Design and implement a simple line editing system. The system provides five sub-editing commands: open file name: The specified file is read into memory　quit: to write back the file being edited file, exit the editing system　list n1- n2: n1 to n2 Display the contents of the line　del row number, column number, the number of characters: delete the specified position from the specified number of characters　ins line number, column number, the string: insert string in the specified location.