The OpenDocument Format (ODF) is an XML-based file format for representing electronic documents such as spreadsheets, charts, presentations and word processing documents. The standard was developed by the OASIS (Organization for the Advancement of Structured Information Standards), and it is free and open format.

The OpenDocument format is used in free software and in proprietary software. Originally, format was implemented by the OpenOffice.org office suite and, with Office 2007 SP2, Microsoft also supports ODF subset.

This article will explain basics of ODF format, and specifically its implementation in spreadsheet applications (OpenOffice.org Calc and Microsoft Office Excel 2007 SP2). Presented is a demo application which writes/reads tabular data to/from .ods files. Application is written in C# using Visual Studio 2008. Created .ods files can be opened using Excel 2007 SP2 and OpenOffice.org Calc.