Microsoft Works is a discontinued office software suite developed by Microsoft and available from 1987-2009. It was often available bundled with Windows computers. This format was a forerunner to other spreadsheet editors with grid of cells arranged in rows and numbers. Versions 1-5 were binary files before the .xlr compound files were developed from version 6 onwards.
11/2023 (v.115)- Description updated. Modified the offset values in the internal signature from null to 0 as part of a project to match PRONOM data with the xsd standard. Internally researched.