| Abbreviation | Definition |
|---|---|
| ALS | Alias - Vivid RayTracer file Bitmap graphics |
| ALT | WordPerfect Library Menu file |
| AMF | Advanced Module Format Music |
| AMG | Actor System image file |
| AMG | AMGC Compressed file archive |
| AMPS | Analysis Of Microelectronic And Photonic Structures |
| AMS | Adobe PhotoShop Adobe Monitor Setup calibration file |
| AMS | Velvert Studio MOD Music file |
| AMX | AMX Mod X |
| AMXX | Amx Mod X extension |
| ANC | Canon Computer Pattern Maker List of pattern colors |
| ANI | Animated cursor (Microsoft Windows) |
| ANI | Animation (Presidio - many) |
| ANM | Deluxe Paint Animator ANiMation file |
| ANN | Windows 3.x Help ANNotations |
| ANS | Animation (graphics or text) |
| ANS | ASCII text with ANSI character set |
| ANT | SimAnt Game data file |
| AOL | America On-Line related file |
| AOS | Installable program (Nokia Communicator add-on software) |