Chapter 2. Managing Workbooks
Save a Workbook
You can save your workbook so you can use it at another time in Excel 2010. Excel 2007 introduced an XML-based file format, and Excel 2010 also uses it. This format reduces the size of a workbook, which improves the likelihood of recovering information if a file becomes corrupted.
By default, Excel 2010 saves new workbooks in the new file format, assigning an extension of .xlsx to the workbook. However, if you open a workbook created in Excel 97-2003, make changes, and then save the workbook, Excel assumes that you want to save the file in the Excel 97-2003 format with a file extension of .xls.
To help you work with others who have not yet upgraded to Excel 2010, you can save a copy of an Excel 2010 workbook ...