| AA | Auto Answer |
| AAB | All-to-All Broadcast |
| AAL | Asynchronous Transfer Mode Adaptation Layer |
| AAP | Applications Access Point |
| AAS | All-to-All Scatter |
| AASP | ASCII Asynchronous Support Package |
| AAT | Average Access Time |
| ABI | Application Binary Interface |
| ABIOS | Advanced BIOS |
| ABIST | Automatic Built-In Self-Test |
| ABLE | Adaptive Battery Life Extender |
| ABR | Available Bit Rate |
| ABRS | Automated Book Request System |
| ABS | Absolute |
| ABT | Abort |
| ABTS | ASCII Block Terminal Services |
| ACC | Accumulator |
| ACD | Automated Call Distribution |
| ACDI | Asynchronous Communications Device Interface |
| ACE | Advanced Computing Environment |
| ACF | Access Control Field or Advanced Communications Function |
| ACH | Automated Clearing House |
| ACIAS | Automated Calibration Interval Analysis System |
| ACIS | American Committee for Interoperable Systems |
| ACK | Acknowledgment |
| ACL | Access Control List |
| ACM | Association for Computing Machinery |
| ACMS | Application Control Management System |
| ACP | Ancillary Control Program or Auxiliary Control Process |
| ACS | Access or Access Control Set or Access Control System |
| ACTS | Automated Computer Time Service |
| ACTT | Advanced Communication and Timekeeping |
| ADCCP | Advanced Data Communication Control Procedures |
| ADD | Automatic Document Detection |
| ADF | Automatic Document Feeder or Automatically Defined Function |
| ADI | AutoCAD Device Interface |
| ADL | Address Data Latch |
| ADLAT | Adaptive Lattice Filter |
| ADLC | Adaptive Lossless Data Compression |
| ADMACS | Apple Document Management and Control System |
| ADMD | Administrative Management Domain |
| ADP | Automatic Data Processing |
| ADPCM | Adaptive Differential Pulse Code Modulation |
| ADR | Address |
| ADS | Application Development Solutions |
| ADSC | Address Status Changed |
| ADSL | Asymmetrical Digital Subscriber Line |
| ADSR | Attack, Decay, Sustain, Release |
| ADT | Application Data Types |
| ADU | Automatic Dialing Unit |
| AE | Above or Equal |
| AEB | Analog Expansion Bus |
| AF | Auxiliary carry Flag |
| AFA | Accelerated File Access |
| AFC | Automatic Font Change |
| AFD | Automatic File Distribution |
| AFII | Association for Font Information Interchange |
| AFIRM | Automated Fingerprint Image Reporting and Match |
| AFIS | Automated Fingerprint Identification System |
| AFS | Andrew File System |
| AFTP | Anonymous File Transfer Protocol |
| AGC | Automatic Gain Control |
| AI | Analog Input or Artificial Intelligence |
| AIA | Applications Integration Architecture |
| AIF | Audio Interchange Format |
| AIIM | Association for Information and Image Management |
| AIN | Advanced Intelligent Network |
| AISB | Association of Imaging Service Bureaus |
| AISP | Association of Information Systems Professionals |
| AIX | Advanced Interactive Executive |
| ALC | Arithmetic and Logic Circuits or Automatic Level Control |
| ALE | Address Latch Enable |
| ALE | Address Latch Enable |
| ALGOL | Algorithmic Oriented Language |
| ALIBI | Adaptive Location of Internet worked Bases |
| ALINK | Active Link |
| ALIWEB | Archie like Indexing in the Web |
| ALN | Asynchronous Learning Network |
| ALR | Advanced Logic Research, Inc. |
| ALT | Alternate |
| ALT. | Alternate lifestyle |
| ALU | Arithmetic Logic Unit |
| AMANDDA | Automated Messaging and Directory Assistance |
| AMD | Active Matrix Display or Advanced Micro Devices |
| AMMA | Advanced Memory Management Architecture |
| AMPS | Advanced Mobile Phone Service |
| ANCOVA | Analysis of Covariance |
| ANI | Automatic Number Identification |
| .ANI | Animated Cursor |
| ANN | Artificial Neural Network |
| .ANN | Annotations |
| ANOVA | Analysis Of Variance |
| ANSI | American National Standards Institute |
| AO | Analog Output |
| AOCE | Apple Open Collaboration Environment |
| AOE | Application Operating Environment |
| AOL | America Online |
| AOS | Add or Subtract |
| AP | Adjunct Processor or Application Processor |
| A/P | Accounts Payable |
| APA | Adaptive Packet Assembly or All Points Addressable |
| APAR | Authorized Program Analysis Report |
| APAREN | Address Parity Enable |
| APCUG | Association of PC User Groups |
| API | Application Program Interface |
| APIC | Advanced Programmable Interrupt Controller |
| APIS | Advanced Passenger Information System |
| APL | A Programming Language |
| APM | Advanced Power Management |
| APP | Application |
| APPC | Advanced Program-to-Program Communications |
| APPI | Advanced Peer-to-Peer Internetworking |
| APPN | Advanced Peer-to-Peer Networking |
| APPS | Applications |
| APRP | Adaptive Pattern Recognition Processing |
| APS | Advanced Photo System or Asynchronous Protocol Specification |
| APSE | ADA Programming Support Environment |
| APT | Address Pass Through or Automatically Programmed Tools |
| A/R | Accounts Receivable |
| ARA | AppleTalk Remote Access |
| ARAG | Antireflective-Antiglare |
| ARCNET | Attached Resource Computer Network |
| .ARJ | Compressed File |
| ARL | Adjusted Ring Length |
| ARLL | Advanced Run Length Limited |
| ARM | Advanced RISC Machine or Annotated Reference Manual |
| ARMA | Association of Records Managers and Administrators |
| ARP | Address Resolution Protocol |
| ARPANET | Advanced Research Projects Agency Network |
| ARPL | Adjust Requested Privilege Level |
| ARTA | Apple Real Time Architecture |
| ARTIC | A Real-Time Interface Compressor |
| ARTS | Asynchronous Remote Takeover Server |
| ARTT | Asynchronous Remote Takeover Terminal |
| ARQ | Automatic Repeat Request |
| ARU | Audio Response Unit |
| AS | Autonomous System |
| ASAP | As Soon As Possible or Automatic Switching and Processing |
| ASCII | American Standard Code for Information Interchange |
| ASIC | Application-Specific Integrated Circuit |
| ASIT | Advanced Security and Identification Technology |
| ASL | Adaptive Speed Leveling |
| ASLM | Apple Shared Library Manager |
| .ASM | Assembler Source Language |
| ASMP | Asymmetric Multiprocessing |
| ASN | Abstract Syntax Notation or Autonomous System Number |
| ASP | Association of Shareware Professionals |
| ASPI | Advanced SCSI Programming Interface |
| ASPS | Advanced Signal Processing System |
| ASR | Address Space Register or Automatic Send-Receive |
| ASYNC | Asynchronous |
| AT | Advanced Technology or Attention |
| ATA | Advanced Technology Attachment |
| ATDP | Attention Dial Pulse |
| ATDT | Attention Dial Tone |
| ATE | Automated Test Equipment |
| ATG | Advanced Technology Group |
| ATH | Attention Hang-Up |
| ATM | Adobe Typeface Manager or Asynchronous Transfer Mode |
| ATPS | AppleTalk Printing Services |
| ATR | Automatic Terminal Recognition |
| ATS | Administrative Terminal System or Apple Terminal Services |
| AT&T | American Telephone and Telegraph |
| ATTN | Attention |
| ATTRIB | Attribute |
| AUDIT | Automated Data Input Terminal |
| AUI | Attachment Unit Interface |
| AUP | Acceptable Use Policy |
| AUTO | Automatic |
| AUTOEXEC | Automatic Execution |
| AUX | Auxiliary |
| AV | Audio/Video or Audiovisual |
| AVA | Audio Visual Authoring |
| AVC | Audio Visual Connection |
| AVG | Average |
| AVI | Audio Visual Interleave |
| AVR | Automatic Voice Recognition |
| AWG | American Wire Gage |
| AWS | Advanced Workstations and Systems |
| AX | Architecture Extended or Automatic Transmission |
