| apx | Lotus Approach Paradox Specific Information |
| aq | Ancestral Quest Database |
| aq1 | AptiQuiz Test |
| aqa | Ancestral Quest Database Index |
| aqa | AptiQuiz Test Result |
| aqc | AquaChem Database |
| aqdb | ANSYS AQWAWB Database |
| aqg | BenMAP Air Quality Grid |
| aqm | AlpineQuest Map |
| aqm | PC 1000 Acquisition Method Data |
| aqp | Articulate Quizmaker 08 Quiz Data |
| aqr | PC 1000 Acquisition Result Data |
| aqtlb | TestComplete Toolbar Settings Data |
| aqz | Amateur Radio Zipped Questionary Data |
| ar-vmp | BrainVoyager QX Anatomical-resolution Volume Map |
| ar0 | MyDOS Ramdisk Image |
| ar1 | MyDOS Ramdisk Image |
| ar2 | MyDOS Ramdisk Image |
| ar3 | MyDOS Ramdisk Image |
| ar4 | MyDOS Ramdisk Image |
| ar5 | MyDOS Ramdisk Image |
| ar6 | MyDOS Ramdisk Image |
| ar7 | MyDOS Ramdisk Image |
| ar8 | MyDOS Ramdisk Image |
| ar9 | MyDOS Ramdisk Image |
| ara | Archivaldo Resource Archive |
| arb | Alphacam Router VB Macro |
| arc | AMPAC Archive File |
| arc | Tinker Archive |
| arca | RealityCharting Chart File |
