- D-R Disconnect and Reconnect
- DAC Digital to Analog Controller
- DAD Desktop Application Director
- DAEMON Disk And Execution MONitor
- DAL Data Access Language
- DAP Data Access Protocol
- DARPA Defense Advanced Research Projects Agency
- DAT Digital Audio Tape / Duplicate Address Test
- DB Destroy Button
- DBA DataBase Administrator
- DBMS DataBase Management System
- DC Direct Current
- DCA Defense Communications Agency
- DCC Direct Cable Connection
- DCD Data Carrier Detect
- DCE Data Communications Equipment / Data Circuit-Terminating Equipment / Device-Control Entries / Distributed Computing Environment
- DCI Display Control Interface
- DCL Delphi Component Library
- DCU Delphi Compiled Unit
- DDA Digital Differential Analyzer
- DDB Device Descriptor Block
- DDC Display Data Channel
- DDCMP Digital Data Communications Message Protocol
- DDE Dynamic Data Exchange
- DDK Device Driver Kit
- DDN Defense Data Network
- DDP Datagram Delivery Protocol
- DDS Digital Data Standard / Digital Data Storage
- DEC Digital Equipment Corporation
- DECmcc DEC management control center
- DEK Data Encryption Key
- DEMPR DEC MultiPort Repeater
- DEN Document-Enabled Network
- DES Data Encryption Standard
- DG Data General
- DI Disable Item
- DIB Device Independent Bitmap
- DID Direct Inward Dial
- DIF Data Interchange Format
- DIP Document Insert Protocol
- DIP Dual In-line Package
- DIX Digital, Intel and Xerox
- DL Data Link
- DLC Data Link Control
- DLCI Data Link Connection Identifier
- DLL Dynamic Link Library
- DLT Digital Linear Tape
- DMA Direct Memory Access
- DMI Desktop Management Interface
- DMT Delphi Menu Template
- DNS Domain Name System
- DOJ Department Of Justice
- dot document template
- DP Dial Pulse
- DPA Demand Protocol Architecture
- DPL Descriptor Privilege Level
- DPMI DOS Protected Mode Interface
- DPP Distributed Parallel Processing
- DPR Delphi PRoject
- DPT Distributed Processing Technology
- DQDB Distributed Queue Dual Bus
- DR-DOS Digital Research Disk Operating System
- DRAM Dynamic Random Access Memory
- DRDA Distributed Relational Database Architecture
- DRP DECnet Routing Protocol
- DS0 Digital Signal Level 0
- DS1 Digital Signal Level 1
- DS3 Digital Signal Level 3
- DSA Directory System Agent
- DSAP Destination Service Access Point
- DSM Distributed System Management
- DSOM Distributable System Object Model
- DSP Digital Signal Processor / Domain Specific Point
- DSR Data Set Ready
- DSSS Direct Sequence Spread Spectrum
- DSTN Dual-Scan Twisted Nematic
- DSU Data Service Unit
- DSU/CSU Data Service Unit/Channel Service Unit
- DTD Document Type Definition
- DTE Data Terminal Equipment
- DTP DeskTop Publishing
- DTR Data Transmit Ready / Data Terminal Ready
- DTSX Data Transport Station for X.25
- DUA Directory User Agent
- DVI Digital Video Interactive
- DXF Drawing EXchange Format
- PI Dots Per Inch