is a format developed by the International Digital Publishing Forum. It is characterized by the XML- and XHTM-based optional use of CSS styling. The main feature of this format is the use of reflowable text (word wrap) which makes it possible to adapt the image to different device displays. The ePub file is a zip-archive with an .epub extension.
XLS format is used to refer to the documents of the program Microsoft Excel. This file is a spreadsheet. All document data distributed and stored in the cells. Each cell has a unique address, which is denoted by letters and Arabic numerals. The cell can contain fixed data, and data in the form of formulas, which bind more cells.