| 11. | .m3a | Sound (MPEG-3 audio) |
| 12. | .m3d | 3d animation macro (Corel Motion) ◊ Sound provider support (Miles 3D Audio) |
| 13. | .m3u | Music playlist (MP3 file URLs) (WinAmp) |
| 14. | .m4 | M4 preprocessor file (unix) |
| 15. | .m7 | Sound (Farallon's MacRecorder format) (sampling rate 7k) |
| 16. | .ma | Ascii file (notebook) (Mathematica) ◊ hDC products for MicroApp executable files (MicroApp) |
| 17. | .ma3 | Macro (Harvard Graphics 3.0) |
| 18. | .mac | Bitmap graphics (black and white Apple MacPaint file) ◊ Macro |
| 19. | .macp | Bitmap graphics B W (Apple Macintosh MacPaint file) |
| 20. | .mad | Module shortcut (Microsoft Access) |
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