The XAR file format has three main regions, The Header, The Table of Contents, and The Heap. The header is a small binary data structure that identifies the file format (file magic). The table of contents is parsed as an XML document. The heap occupies the remainder of the file. Files' data are stored in the heap.
Microsoft Excel now has a built-in AutoRecover feature that has replaced the AutoSave add-in that exists in versions of Excel that are earlier than Microsoft Excel 2002. The AutoRecover feature saves copies of all open Excel files at a user-definable fixed interval. The files can be recovered if Excel closes unexpectedly, for example, during a power failure.
XAR is a vector file format which is native to Xara X and other Xara applications.