| 1. | .ad | Screensaver (AfterDark) |
| 2. | .ad2 | ADPCM 2-bit compressed voice file (ZFAX) |
| 3. | .ad3 | ADPCM 3-bit compressed voice file (ZFAX) |
| 4. | .ada | Ada language source code file |
| 5. | .adb | Ada Package Body ◊ Advanced database (Microtech) ◊ Appointment database (HP 100LX organizer) |
| 6. | .adc | Bitmap graphics (16 colors) (ScanStudio) ◊ Dictionary (Lingvo) ◊ Sound (TI/MIT ADC format) |
| 7. | .add | Adapter Device Driver (OS/2) ◊ Additional information |
| 8. | .ade | Audio file (ADC,TI/MIT) |
| 9. | .adex | Bitmap graphics (ADEX Corp. image file) |
| 10. | .adf | ARC/INFO coverage data file (ArcView) ◊ Administration configuration file ◊ Amiga Disk File |
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