| apr | SAM Alignment Probabilities Data |
| apr_lib | Altium Designer Aperture Library Data |
| apsmartalbum | Apple Aperture Smart Album Data |
| apt | Alphacam Punch Tool Data |
| apt | Gerber Aperture Data |
| apt | Nimbus 7 SAMS APRIORI Data |
| apv | EdiAPV Data |
| apvault | Apple Aperture Vault Data |
| apversion | Apple Photos Version Data |
| apvolume | Apple Photos Volume Data |
| apvr | BenMAP APV Configuration Results |
| apw | AnyPassword Data File |
| 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 |
