Convert OpenOffice.org Calc spreadsheets into a Microsoft Excel file to take advantage of Excel's built-in tools. OpenOffice.org spreadsheets default to a .xsc file extension, which certain versions ...

XLS files are Excel workbook files created in Excel 97 or Excel 2003. The 2007, 2010 and 2013 versions of the program use the XLSX format by default to save workbooks, but can also use the XLS format.

In the Mac OS it is possible to change the default program the operating system will use to open a file when you double-click on it. After you have changed this file association, though, you may want ...