| ask | AskSam Database |
| ask | Ableton Live Skin |
| asl | Miranda IM Emotions Definition |
| aslquery | Mac OS X Console Query |
| asm | Alphacam Stone Param Macro |
| asmdot | SolidWorks Assembly Template |
| asmprp | SolidWorks Assembly Properties Template |
| asn | NCBI ASN.1 Data |
| asn | Abstract Syntax Notation One Data |
| asn1 | Abstract Syntax Notation One Data |
| asp | Alphacam Stone Post Data |
| asp | MGS Antenna SPK File |
| assetproj | Camtasia Studio Asset Information |
| assoc | Associate This File Association Database |
| asstore | Microsoft SQL Server Property String Store |
| assy | Siemens NX Assembly Data |
| ast | Adobe Color Separation Table |
| ast2 | Astrotite 200X Data |
| astm | Optitex 3D Suite ASTM Grading File |
| astore | Microsoft SQL Server Property Main Store |
| astore | LUX Variables Data |
| asu | Toolbook Package Definition |
| asv | MakeMusic Finale Auto-save File |
| asvx | MakeMusic Finale Auto-save File |
| aswcs | Avast Compressed Skin |
| asws | Avast Skin |
| asy | Xilinx CORE Generator Graphical Symbol File |
| at1 | KJT-200 Absorbance Data |
| atb | Alphacam Lathe VB Macro |
| atc | AceText Collection File |
| atc | Autodesk AutoCAD Tool Catalog |
| atc | AttacheCase Encrypted File |
| atc_list | aTube Catcher Data |
| atf | GenePix Axon Text File |
| atf | ASAM Transfer Format XML Data |