Microsoft Office Excel (2007+) Spreadsheet (Macro Enabled)
Files with the XLSM extension are associated with Microsoft Excel, versions 2007 and above. Microsoft Excel is compatible with multiple operating systems and it's currently one of the top applications for creating and editing spreadsheets.
The XLSM format stores data in worksheets. Each worksheet has a grid of cells arranged in columns and rows. Cells can contain text and numbers of various fonts, colors and sizes. XLSM files may also include charts, pivot tables, graphs and mathematical functions. Microsoft Excel also features the Visual Basic macro programming language for applications.
Additionally, XLSM files can also store Macros. Embedding them into the document's structure is done via the Macro Recorder included in MS Office which can save command sequences and create macros to replicate them automatically.
XLSM files are based on the Open XML format which stores all content in a zipped archive. The archive contains XML and RELS files stored in three separate folders named “docProps”, “xl” and "_rels". Files with the RELS extension dictate how the parts of the document connect to form a single file. The archive also includes a [Content_Types].xml file which describes the spreadsheet and separate XML files for each worksheet. This archived approach makes file content more accessible. For example images and text are stored individually within the archive.