The standard extension for Excel workbooks is xls for versions up to 2003. Excel 2007 uses xlsx as its extension for workbooks.
XLS is the filename extension for a Microsoft Excel Workbook.
xlsx
Open Microsoft Excel and start making your workbook. When you are done, save the workbook. Or, if you are already editing a workbook, click "new..." (file-->new... in M.E. 2003) to create a new workbook.
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yes
A workbook, in Microsoft Excel, is what they call the spreadsheet(s). Just as in Microsoft Word, the page you are writing is called the document.
In Microsoft Excel, a new workbook will normally have three worksheets.
.XLSX
In Microsoft Excel, a new workbook will normally have three worksheets.
auto save
It is a macro-enabled workbook from Office 2007.
For a new workbook, it is cell A1 on Sheet1. If you open a workbook that you already have, then whatever was selected when it was saved will still be selected.