In Windows, what do you get if you change the extension of an (unprotected) Excel file from .xlsx to .zip?
- A file that MS EXCEL cannot open
- Nothing useful at all
- A corrupt ZIP file
- The original spreadsheet as a set of XML files within the ZIP
EXPLANATION
Since Office 2007 Microsoft has used Open XML to store non-password protected documents. These are then combined into a single compressed file usingthe docx, xlsx, pptx, etc. extensions. Even though the XML files are quite large, they compress very well.