SAP developers may create 4 kind of files for Excel:
- Native Excel files (those you obtain when you "Save As" "Microsoft Office Excel Workbook"), using OLE (or DOI abstract layer)
- Excel files - CSV format
- Excel files - XML format
- XLSX (zipped file containing XML, compliant with "Office Open XML" format). The abap2xlsx project can be used to create .XLSX files in ABAP only.