XLS (Microsoft Excel Spreadsheet)
The XLS Spreadsheet file format
XLS is the file format extension for Microsoft Excel files. The XLS extension was used until the 2007 version of Excel and was replaced by an Open Office XML file format (XML Spreadsheet, or XMLSS). Excel 2007 is backwards compatible and reads many file formats from DOS-based programs. Excel is often used by third-party applications (like browsers) to avoid implementing the use of binary file formats. XLS files contain spreadsheet information and hold the worksheets, charts, calculations, tables, and macros. This file extension was also used in the Visual Basic programming language. Excel is part of Microsoft Office and available for both Microsoft Windows and Mac OS.
Technical details of XLS files
XML Spreadsheets are missing some advanced features (like storage of VBA macros) but it is used for its simplicity. Before 2007, Excel used a proprietary binary file format (Binary Interchange File Format/BIFF) for formatting. This allows the user to alter the workbook templates and individual workbook content. Legacy formats which can be ready by Excel include: CSV, DBF, SYLK, and DIF. XLS was replaced by file extensions like XLSX, XLSM, and XLSB. Upon the replacement of XLS files, Excel 2007 remained backwards compatible, meaning the XLS file extension is still very useful.