- SAA Systems Application Architecture
- QABME Set Asynchronous Balanced Mode Extended
- SAP Service Access Point / Service Advertising Protocol
- SATAN Security Analysis Tool for Auditing Networks
- SCAM SCSI Configuration AutoMagic / SCSI Configured AutoMatically
- SCC Serial Communications Controller
- SCMS Serial Copy Management System
- SCO Santa Cruz Operations
- SCS System Communication Services
- SCSI Small Computer Systems Interface
- SD Send Data
- SDC Secondary Domain Controller
- SDD Software Description Database
- SDI Single Document Interface
- SDK System Design Kit / System Development Kit
- SDLC Synchronous Data-Link Control
- sea self-extracting archive
- SEAM Saber Enterprise Application Manager
- SED Stream EDitor
- SEF Source Explicit Forwarding
- SGI Silicon Graphics Incorporated
- SGML Standard Generalized Markup Language
- SGMP Simple Gateway Management Protocol
- shar shell archives
- SHED Segmented Hypergraphics EDitor
- SHG Segmented HyperGraphics
- SIG Special Interest Group
- SIMM Single In-line Memory Module
- SIPS SMDS Interface Protocol
- SIR Serial InfraRed
- SLIP Serial Line Internet Protocol
- SM Standby Monitor
- SMART Software Metering and Resource Tracking
- SMB Server Message Block
- SMDS Switched Multimedia Data Services / Switched Multimegabit Data Service
- SMFA Specific Management Functional Area
- SMI Structure of Management Information
- SMP Symmetric MultiProcessing
- SMS Storage Management Services / Systems Management Server
- SMTP Simple Mail Transfer Protocol
- SNA Systems Network Architecture
- SNADS Systems Network Architecture Distribution Services
- SNAP Sub-Network Access Protocol
- SNI Subscriber Network Interface
- SNMP Simple Network Management Protocol
- SOH Start Of Header
- SOHO Small Office Home Office
- SOM System Object Model
- SONET Synchronous Optical NETwork
- SP Stack Pointer
- SPA Software Publishing Association
- SPARC Scaleable Performance ARChitecture
- SPEC Systems Performance Evaluation Cooperative
- SPOOL Simultaneous Peripheral Operations Off-Line
- SPP Sequenced Packet Protocol
- SPR Statistical Pattern Recognition
- SPX Sequenced Packet EXchange
- SQL Structured Query Language
- SR Source Routing
- SRAM Static Random Access Memory
- SRBs Source Routing Bridges
- SRF Specifically Routed Frame
- SRI Stanford Research Institute
- SRT Source Routing Transparent
- SSAP Source Service Access Point
- SSL Security Systems Layer
- STAR Shareware Trade Association and Resources
- STE Spanning Tree Explorer
- STID STation ID
- STN Super-Twisted Nematic
- STP Shielded Twisted Pair
- SUA Stored Upstream Address
- SVC Switched Virtual Circuit
- SVD Simultaneous Voice and Data
- SVGA Super Video Graphics Array
- SWAIS Single Wide-Area Information System