Using the New Microsoft Office File Format
Starting with the 1997 release, all Microsoft Office programs have used a binary file format that computers (but not humans) can read. Excel 2007, Microsoft Office Word 2007, and Microsoft Office PowerPoint® 2007 have a new and improved file format that, in addition to being somewhat readable, creates much smaller files than the older binary format.
The new Microsoft Office Open XML Formats combine the XML and the Zip file compression format to create robust files that (on average) are about half the size of similar Excel 972003 files. You can open and save Excel 972003 files in Excel 2007, of course. If you want to open Excel 2007 files in Excel 2000, Excel 2002, or Excel 2003, you can install the Microsoft Office Compatibility Pack for Office Word 2007, Excel 2007, and Office PowerPoint 2007 file formats from this book's companion CD.
Besides smaller file sizes, the 2007 Microsoft Office system file formats offer several other advantages:
Improved interoperability. Because the new file formats use XML as their base, it is much easier for organizations to share and exchange data between the Microsoft Office system programs and other applications. The older binary file format was difficult to read and wasn't standards-based.
Enhanced customization. The letter "X" in XML stands for "extensible," which means that information professionals and developers can create custom document structures, or schema, that meet their organization's needs.
Improved automation. The Excel 2007 file format is based on open standards, which means that any program written to process data based on those standards will work with Excel 2007. In other words, you don't need to write special routines or use another program in the Microsoft Office system to handle your Excel 2007 data programmatically.
Compartmentalizing information. The new Microsoft Office system file format separates document data, macro code, and header information into separate containers, which Excel 2007 then combines into the file you see when you open your workbook. Separating macro code (automated program instructions) from your worksheet data improves security by identifying that a workbook contains a macro and enables you to prevent Excel 2007 from executing code that could harm your computer or steal valuable personal or business information.