File Extension Xlsx

Microsoft introduced new file formats for all applications in its 2007 Office Suite. Among them is the .xlsx format and extension for Excel workbooks. All of these new formats are based on XML, and Microsoft claims the new formats will be open for anyone to use. This action was a response to a worldwide call for an open standard for all documents in order to make international business communications easier. Rather than being open, Microsoft's XML based formats are in fact, proprietary and still protected, though the company has made them more open than they have in the past.


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The .xlsx extension is used specifically for Excel workbooks that contain no macros. For those that do contain them, the extension is changed to .xlsm. Microsoft has followed this same system for all of its Office formats; where the letter “m” is in the extension, macros are being used in the document. File converters are available from Microsoft to enable earlier versions of Office to open these new file formats. It has been reported that the converters are not offered for versions earlier than Office 2000.

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More Info Regarding File Extension Xlsx

Microsoft has stated several benefits to using the new .xlsx format including reduced file size, increased security, improved interoperability between Office products, and better file recovery technology. In terms of the file size issue, it is reported that the new .xlsx file can be up to 75% smaller than previous .xls files. Excel automatically compresses the .xlsx file (using ZIP compression) when the file is saved, and uncompresses it when it is re-opened. The compression allows for easier and quicker transfer of files between computers or over a network.

The .xlsx format is essentially a container but Microsoft has introduced new terminology to reflect its new open formats. Instead of calling their structure a container, they have chosen the word “package”. Inside the package are three groups of “parts”. The first group contains three individual parts that store information about document properties, application properties, and customized document properties. The second group contains the data for the individual worksheets, while the third group stores information about styles, charts, and strings. The third group of parts is stored relationally to each individual worksheet.

Errors with .xlsx files are the same as one would expect from any data file. Corrupt data can cause Excel to not display the worksheets correctly, it might not load the document at all, or it could cause a software crash. Corrupt data in an .xlsx file is unlikely to cause any significant damage to the operating system. The most common error with these files is caused when importing the documents into non-Microsoft spreadsheet applications. Though may other packages claim support for the .xlsx file, the conversion in most cases does not go perfectly. In some cases users will get an “unable to open” error. Individuals should check with their software developer to see if there are any updates or bug fixes to address the problem.

Windows users have the most options for programs that open .xlsx files including Microsoft Excel 2007, Excel 2000, XP, and 2003 (with converters installed), OxygenOffice Professional, Calc, and Panergy docXConverter. Mac Users can choose from Microsoft Excel 2008, Apple Numbers, Calc, and Panergy docXConverter. For Linux systems there is OxygenOffice Professional and Calc.

Other third party conversion programs are available such as Batch XLS and XLSX Converter. This program does just what its name implies; it allows for batch conversion of dozens of file formats including .xls and .xlsx. The program is Windows only, for XP, 2000, 98, and ME. Another Windows only conversion program is Convert XLS from Softinterface, Inc. Users who prefer on on-line conversion service can try Zamzar or SheetConvert.

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