The X Factor - File Changes introduced in Microsoft Office 2007 and Preserved Henceforth

MS Office 2007 introduced new file extensions - XLSX for Excel, PPTX for Powerpoint and DOCX for Word. These are generally smaller in size than their pre-Office 2007 equivalents. These use Office XML. So, for example, a PPTX file would an XML-based Powerpoint presentation. Note that these file formats disallow macros. The corresponding macro-enabled versions all have the X replaced with an M - hence we have XLSM for a macro-enabled Excel workbook, PPTM for a macro-enabled Powerpoint presentation and DOCM for a macro-enable Word document. In theory, these XML formats allow the files to be consumed by a variety of applications, not just Word, Excel or Powerpoint and allow batch processing software to be built, for example processing automatically hundreds of Word documents.