Final answer:
The '.xls' is the file extension that informs the operating system and users about the file type, which in this case is an Excel spreadsheet, and indicates the software to be used to open it.
Step-by-step explanation:
The '.xls' in the path 'C:UsersDoeDocumentsmyfilesmyBook. xls' is referred to as a file extension. A file extension is a suffix at the end of a computer file that indicates the file's format and determines which program will open it. In this case, '. xls' denotes that the file is an Excel spreadsheet, and it would typically be opened with Microsoft Excel or another compatible spreadsheet program.
The extension helps both users and the operating system recognize the file type and ensures that the file is associated with the appropriate software for editing or viewing. File extensions usually consist of three or four characters that follow the dot at the end of the filename, though they can sometimes be longer.
For example, if a file is named 'report. pdf', the '. pdf' extension indicates that it's a Portable Document Format file, and it would generally be opened by PDF reader software. Different extensions correspond to different file types such as '. docx' for Microsoft Word documents or '. jpg' for image files.