| 81. | .mes | Macro Editor work space file (WordPerfect Library) ◊ Message ◊ Music (RealJukebox) |
| 82. | .met | Document (Omnipage Pro) ◊ Macro Editor top overflow file (WordPerfect Library) ◊ Metafile (OS/2) |
| 83. | .meu | Menu group (DOS Shell) |
| 84. | .mex | Dynamically linked subroutines (Macintosh) (Matlab) ◊ Macro Editor expound file (WordPerfect Library) |
| 85. | .mex4 | Dynamically linked subroutines (Sun-4/SPARC) (Matlab) |
| 86. | .mexds | Dynamically linked subroutines (DECStation) (Matlab) |
| 87. | .mexhp3 | Dynamically linked subroutines (HP9000/series 300) (Matlab) |
| 88. | .mexhp7 | Dynamically linked subroutines (HP9000/series 700) (Matlab) |
| 89. | .mexn | Dynamically linked subroutines (NeXT) (Matlab) |
| 90. | .mexrs6 | Dynamically linked subroutines (IBM RS/6000) (Matlab) |