xls The .xls filename extension is a native binary file format associated with the closed source spreadsheet application Microsoft Office Excel. First introduced in 1987 with the release of Excel 2.x, the file format acts as the container for storing spreadsheet data such as work sheets, charts, and macros. Prior to Microsoft Office Excel 2007, the xls binary format was the default standard for the Microsoft Office Excel until the later adoption of the Open Document standard .xlsx. Documents to be saved in the .xls format are saved as Excel 97, 2003 documents.
ods The Open Document spreadsheet filename extension format is an alternative open source spreadsheet file format and is part of the larger OpenDocument family of open source file formats. The format is associated with documents where tabular or spreadsheet information is represented. Several proprietary and open source applications are compatible with the format, allowing for interoperability between software systems that support the OpenDocument format. Proprietary applications such as in Microsoft Office Excel 2007 and above can open .ods files however certain proprietary features in Microsoft Office Excel may not be compatible with the format. Other open source spreadsheet applications (such as OpenOffice) support the .ods filename extension in its entirety.