| Acronym | Meaning |
 | A/D | Analog To Digital |
| A/V | Audio/Visual |
| AAC | Advanced Audio Coding |
| AARP | AppleTalk Address Resolution Protocol |
| ABBH | Average Bouncing Busy Hour |
| ABC | Atanasoff-Berry Computer |
| ABEND | Abnormal End |
| AC | Alternating Current |
| ACD | Automatic Call Distributor |
| ACES | Asia Cellular Satellite System |
| ACK | Acknowledge Character |
| ACL | Access Control List |
| ACM | Association For Computing Machinery |
| ACPI | Advanced Configuration And Power Interface |
| ACTA | America's Carriers Telecommunications Association |
| ACU | Automatic Calling Unit |
| ADB | Apple Desktop Bus |
| ADCCP | Advanced Data Communications Control Protocol |
| ADO | ActiveX Data Objects |
| ADP | Automatic Data Processing |
| ADPCM | Adaptive Differential Pulse Code Modulation |
| ADS | Alternate Data Streams |
| ADSL | Asymmetric Digital Subscriber Line |
| ADVEIS | Anti-Virus Dependent Vulnerabilities In E-mail Infrastructure Security |
| AES | Asynchronous Event Scheduler |
| AFAIK | As Far As I Know |
| AGP | Accelerated Graphics Port |
| AH | Authentication Header |
| AI | Artificial Intelligence |
| AIFF | Audio Interchange File Format |
| AIFF-C | Audio Interchange File Format |
| AIML | Astronomical Instrument Markup Language |
| AIX | Advanced Interactive Executive |
| ALGOL | Algorithmic Language |
| ALU | Arithmetic (and) Logic Unit |
| AMANDA | Advanced Maryland Automatic Network Disk Archiver |
| AMD | Advanced Micro Devices |
| AML | Astronomy Markup Language |
| AMP | Advanced Metal Powder |
| AMPS | Advanced Mobile Phone System |
| AMS | American Mobile Satellite Corporation |
| AN | Active Network |
| ANSA | Adaptive Network Security Alliance |
| ANSI | American National Standards Institute |
| AOL | America Online |
| APA | All Points Addressable |
| API | Application Program(ming) Interface |
| APM | Advanced Power Management |
| APP | Application Portability Profile |
| APWG | Anti-Phishing Working Group |
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