| aqp | Articulate Quizmaker 08 Quiz Data |
| aqr | PC 1000 Acquisition Result Data |
| aqtlb | TestComplete Toolbar Settings 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 |
| arcade | GameSpy Arcade Data |
| architect | BSS Soundweb London Design Data |
| arcut | Adobe Prelude Rough Cut Data |
| arcutx | Adobe Prelude Rough Cut Data |
| arescol | Ares Galaxy Collection List |
| arf | WebEx Advanced Recording |
| arff | Weka Attribute-Relation File Format |
| arg | Autodesk AutoCAD User Profile |
| arlnk | Ares Galaxy Link Data |
| arm | Alphacam Router Param Macro |
| arm | Armadillo Protected File |
| armodel | Kudan AR Model |
| arp | Alphacam Router Post Data |
| arpack | ArtRage Package File |
| ars | Adobe After Effects Render Settings |
| arscript | ArtRage Script File |