An m99 file extension is related to the M99 compressed data file format.
M99 file extension - M99 compressed data
What is m99 file? How to open m99 files?
File type specification:
The m99 file extension is associated with the data compression algorithm represents and entirely new class of statistical compression that is unreleated to other statistical encoding techniques such as Huffman and Arithmetic coders.
This m99 file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.