| AA | Antialiasing |
| AAA | authentication, authorization and accounting, siehe Triple-A-System |
| AAD | Azure Active Directory |
| AAC | Advanced Audio Coding |
| AACS | Advanced Access Content System |
| AAL | ATM Adaptation Layer |
| AAM | ATA/ATAPI Architecture Model |
| Automatic acoustic management |
| ACC | Adaptive Computing Controller (SAP) |
| ACE | ASCII Compatible Encoding |
| Access Control Entry (Eintrag in der Access Control List) |
| ACK | acknowledge 'bestätige', siehe ACK (Signal) und Netzjargon |
| ACL | Access Control List |
| ACPI | Advanced Configuration and Power Interface |
| ACR | Advanced Communication(s) Riser oder |
| Automatic carriage return oder |
| Attenuation To Crosstalk Ratio |
| ACS | Applied Computer Science (Angewandte Informatik) oder |
| ATA/ATAPI Command Set (siehe ATA/ATAPI) |
| AD | Active Directory |
| ADAM | Active Directory Application Mode |
| ADAPT | Application Design for Analytical Processing Technologies |
| ADB | Apple Desktop Bus oder |
| Android Debug Bridge |
| ADC | Apple Display Connector (Variante von DVI) |
| ADDS | Active Directory Domain Services (Erweiterung des früheren Verzeichnisdienstes ADS von Microsoft) |
| ADO | ActiveX Data Objects |
| ADS | Automated Deployment Service oder |
| Alternate Data Streams |
| ADSL | Asymmetric Digital Subscriber Line, Variante von DSL |
| ADSP | AppleTalk Data Stream Protocol |
| AEG | Ausschalten, einschalten, geht, Tipp zur Problemlösung |
| AEP | AppleTalk Echo Protocol |
| AES | Advanced Encryption Standard |
| AF | Anisotropes Filtern |
| AFK | Away from Keyboard |
| AFP | Apple Filing Protocol |
| AGA | Advanced Graphics Architecture (Amiga-Chipsatz) |
| AGESA | AMD Generic Encapsulated Software Architecture |
| AGP | Accelerated Graphics Port |
| AGU | Address Generation Unit |
| AHCI | Advanced Host Controller Interface |
| AI | Artificial Intelligence (Künstliche Intelligenz, deutsche Abkürzung: KI) |
| AIA | Authority Information Access |
| AIFF | Audio Interchange File Format |
| AIM | AOL Instant Messenger |
| AIR | Adobe Integrated Runtime |
| AIT | Advanced Intelligent Tape |
| AJAX | Asynchronous JavaScript and XML |
| aka | also known as (auch bekannt unter dem Namen …), siehe: Pseudonym |
| ALM | Application Lifecycle Management (u. a. von Borland) |
| ALSA | Advanced Linux Sound Architecture |
| ALU | Arithmetisch-logische Einheit (arithmetisch-logische Einheit, Teil einer CPU) |
| AMD | Advanced Micro Devices |
| AMQP | Advanced Message Queuing Protocol |
| ANSI | American National Standards Institute; auch ANSI-Escapesequenz, vgl. ANSI.SYS |
| AOP | Aspektorientierte Programmierung |
| AOSP | Android Open Source Project |
| AP | Access Point |
| APDU | Application Protocol Data Unit |
| API | Application Programmers/Programming Interface oder |
| Adaptive Planungsintelligenz |
| APIC | Advanced Programmable Interrupt Controller |
| APIPA | Automatic Private IP Addressing |
| APL | A Programming Language |
| APL | Abschlusspunkt Linientechnik |
| APM | Advanced Power Management |
| APOP | Authenticated Post Office Protocol |
| APP | Application (Applikation) |
| APU | Accelerated Processing Unit |
| AQE | Augmented Quad Edge (Datenstruktur zur Speicherung und effizienten Traversierung eins 3D Voronoi-Diagramms) |
| AR | Augmented Reality |
| ARM | Advanced RISC Machines Ltd. oder |
| Application Response Measurement |
| ARP | Address Resolution Protocol |
| ARQ | Automatic Repeat reQuest |
| ARS | Adaptive Rate Selection |
| ASCII | American Standard Code for Information Interchange (amerikanische Standardkodierung für den Informationsaustausch) |
| ASIC | Application-Specific Integrated Circuit (anwendungsspezifische integrierte Schaltung) |
| ASN.1 | Abstract Syntax Notation One |
| ASP | Active Server Pages oder |
| Application Service Providing oder |
| AppleTalk Session Protocol |
| ASPI | Advanced SCSI Programming Interface |
| AT | Advanced Technology (Bauform für Mainboards und Gehäuse) |
| ATA | Advanced Technology (AT) Attachment |
| ATAPI | AT-Attachment Packet Interface |
| ATM | Asynchronous Transfer Mode oder |
| Asynchronous Time Multiplexing oder |
| Adobe Type Manager |
| ATPG | Automatic Test Pattern Generation |
| ATX | Advanced Technology Extended |
| AUI | Attachment Unit Interface |
| AV | Anti-Virus |
| AVI | Audio Video Interleave |