| Abbreviation | Definition |
|---|---|
| AR | Automatic Reset |
| ARCA | Advanced Recovery Continuity Appliance |
| ARI | Automated Reset Indication |
| ARM | Acorn RISC Machine |
| ARMD | ATAPI (Advanced Technology Attachment with Packet Interface) Removable Media Device |
| ARMS | Active Real-time Machine System |
| ARMS | Advanced Reticle Management System |
| ART | Audio Response Terminal |
| ARTS | Analog Real-Time Synthesizer |
| AS | Accelerated Standard |
| AS | Autonomous System |
| ASA | Advanced Speaker Array |
| ASB | Advanced System Bus |
| ASC | Accessory Switch Controller |
| ASCK | Asynchronous Serial Clock |
| ASD | Adjustable Speed Drive |
| ASD | Apple Service Diagnostic |
| ASD | Apple Service Diagnostics |
| ASDP | Automation of Structure Determination Platform |
| ASF | Architecture Simulation Framework |