While it is technically possible to open an Excel file in Notepad, this is not a good idea. Excel files are binary files that contain complex formatting and data structures. When you open an Excel ...

Also known as a Comma Separated Value file, a comma delimited file is a standard file type that a number of different data-manipulation programs can read and understand, including Microsoft Excel.

For example, you can save contact information from Microsoft Excel as a CSV file, and import it into the address book in Microsoft Outlook.