One of my favorite blog posts from Joel Spolsky talks about this, basically explaining how these formats come to be. For mega-softwares like those, the source c

One of my favorite blog posts from Joel Spolsky talks about this, basically explaining how these formats come to be. For mega-softwares like those, the source code is the de facto file spec www.joelonsoftware.com/items/2008/02/19.html