Word Documents Used to Be Filesystems

Last post ended on a promise: a .docx is a ZIP file, and you already know how ZIP works. That's true, and it's the smaller half of the story. The interesting part is what .docx replaced, because the old .doc format was doing something strange. It wasn't a document. It was a filesystem with a document living inside it. A Filesystem in a File Here's a real .doc from 2015, 10,240 bytes. The first…