| a7e | Macromedia Authorware Packaged Library |
| a7l | Macromedia Authorware Library |
| a7m | Macromedia Authorware Macintosh File |
| a7p | Macromedia Authorware Source |
| a7w | Macromedia Authorware Windows File |
| a86 | A86 Assembly Souce Code |
| aah | Amazingly Abstracted HTML Document |
| aapkg | ArchestrA IDE Package |
| ab | Applix Builder Data |
| ab2 | Blitz Basic Code |
| abap | ABAP Source Code |
| abn | Alpha Five Database Export |
| abo | Applix Builder Object |
| ac | GNU Autoconf Input File |
| acme | ACME Assembler Source Code |
| acsup | Avaya CMS Script |
| actx | DS Game Maker Action Description |
| acu | ACUCOBOL-GT Compiled Program |
| ad | DSM Application Diagram |
| ada | Ada Source Code |
| adb | Ada Implementation File |
| adb | Alpha Five Database |
| adblock | Alpha Five Database Lock |
| adls | ADL Source File |
| adpp | Adobe Device Central Profile Package |
| ads | Ada Specification File |
| advs | Adobe Device Central Device Set |
| ael | Asterisk Extension Language Source Code |
| aex | Alpha Five Compiled Library Script |
| agc | AfterGRASP Compiled Script |
| agi | Asterisk Gateway Interface |
| agls | Adobe GoLive Snippet |
| ago | Autolog Script |
| agq | Altair GraphQL Client Data |
| agwl | Abstract Grid Workflow Language Data |