.XLS file extension is created by Microsoft. .XLS has been classified as Spreadsheet Files. The format of .XLS file is Binary.
An XLS file is a spreadsheet file created by Microsoft Excel or exported by another spreadsheet program, such as OpenOffice Calc or Apple Numbers. It contains one or more worksheets, which store and display data in a table format. XLS files may also store mathematical functions, charts, styles, and formatting.
XLS file open in Microsoft Excel 2016
A spreadsheet is used for organizing, analyzing, manipulating, and visualizing data. It consists of a table with rows and columns. The table cells may contain manually entered data or the results computed from the data of other cells.
Excel is the most widely used spreadsheet application in the world. It comes with every edition of the Microsoft Office suite and is used in home, academic, and business environments. If you work in an office environment, there is a good chance you have seen and opened an XLS file.
NOTE: XLS files are saved in the Excel Binary File Format, which was the primary format until the Office Open XML format was introduced with Excel 2007. Most Excel files are now saved in the Office Open XML format, with an .XLSX file extension. However, Microsoft Excel an many other spreadsheet programs still support the older XLS format.
Common XLS Filenames
Workbook1.xls - The default filename Microsoft Excel gives to new spreadsheets prior to Excel 2007, which creates new spreadsheets with the Workbook1.xlsx filename.