| Abbreviation | Definition |
|---|---|
| A.D./B.C. | Macintosh Assembly Source Code |
| A00 | Archive Section of a file distributed by archives |
| A01 | ARJ Multi-volume Compressed Archive |
| A01 | OzWin CompuServe E-mail/Forum Access SYSOP File |
| A10 | OzWin CompuServe E-mail/Forum Access SYSOP File |
| A11 | AIM Graphics file |
| A21 | Soundweb Firmware File |
| A2A | APLASCII EISPACK file |
| A2A | IBM Voice Type Language Vocabels File |
| A2A | Sharp APL Workspace Export File |
| A2B | A2B Player Playlist |
| A2M | AudioToMidi Settings file |
| A3 | Unrelated Inventions Audiotools Show Log |
| A3D | Amapi 3D Modeling File |
| A3K | Yamaha A3000 Sampler File |
| A3L | Authorware Version 3.x Library |
| A41 | Authorware Version 4.x Library |
| A4L | Authorware Version 4.x Library |
| A4P | Authorware File Without Runtime |
| A5W | Unpackaged Authorware Windows File |