Starting with Office 2007, Microsoft switched to Office Open XML (OOXML) as the default file formats for its applications. However, the legacy .doc (Word), .xls (Excel) and .ppt (PowerPoint ...
See Office file formats and ECMA. An Office Open XML (OOXML) document is a zipped (compressed) collection of folders, subfolders, XML files and other file types, which is a huge contrast from ...