File Extension XLS
File extension XLS is most commonly associated with Microsoft Excel, a popular spreadsheet application, and are used to store workbooks which can contain one or more individual spreadsheets. XLS files are a proprietary format called Binary Interchange File Format (BIFF), and is the default extension used by Microsoft Excel up until Office 2007.
XLS files contain data in spreadsheet format which is organised in rows and columns. Each individual data item is stored in a cell, which can be uniquely referenced using the column letter and row number. XLS files are used primarily to store numerical data, and can also contain formulas, charts and graphs, which alter dynamically to reflect the source data. XLS files also support embedded objects from other applications as well as text formatting and images to enhance the presentation of data stored in spreadsheets. XLS files are widely used in any application that involves the storing and manipulation of numerical data, such as budgeting, accountancy and scientific research.
Care should be taken when opening XLS files, particularly from unknown sources, as they may contain a potential security risk in the form of macros. Macros are scripts which are either written in a programming language called Visual Basic for Applications (VBA), or recorded as a series of instructions based on user keyboard and mouse input. Though macros are intended to reduce the need to perform repetitive tasks, they can also be written for malicious or destructive purposes.
A similar albeit less popular format similar to XLS is Corel Quattro Pro's File extension QPW file format, which is also used to store multiple spreadsheets in a workbook. QPW files are a proprietary format which can only be opened using Corel Quattro Pro, part of the Corel WordPerfect Office suite, though data can be exported to other more widely supported formats such as XLS or CSV for use in other applications.
XLS files are native to Microsoft Excel, though can also be opened using other spreadsheet applications such as OpenOffice.org Calc or Corel Quattro Pro. Alternatively, the data contained within an XLS file can be viewed and printed using Excel Viewer, though this will not allow editing. As of Microsoft Office 2007, a new XML-based format using the extension File extension XLSX was introduced as the native Excel format, though XLS files are still fully supported.