UA        User Agent , User Area
UAE       Unrecoverable Application Error
UART      Universal Asynchronous Receiver/Transmitter
.UC2      Compressed File (file name extension) [UltraCompressor]
UCL       Universal Communications Language
UCS       Unicode Conversion Support , Universal Character Set ,
          User Coordinate System
UCT       Universal Coordinated Time
UDC       User Defined Commands
UDE       Universal Data Exchange
UDF       User Defined Functions
UDG       User Defined Gateway
UDP       User Datagram Protocol
UDT       Uniform Data Transfer
UFS       Unix File System
UG        User Group
UI        Unix International , User Interface
UID       User Identifier
UIMS      User Interface Management System
UL        Underwriters Laboratories ,
          Unordered List , Upload
ULA       Uncommitted Logic Array
ULN       Universal Link Negotiation
ULSI      Ultra Large Scale Integration
UMA       Unified Memory Architecture
UMB       Upper Memory Block [LIM/AST]
UNC       Universal Naming Convention ,
          Uuencoded Netnews Collator [Unix]
UNCOL     Universal Computed Oriented Language
UNI       User-Network Interface
UNICOM    Universal Integrated Communication (System)
UNICOS    Universal Compiler FORTRAN compatible
UNIVAC    Universal Automatic Computer
UNIX      (AT&T Bell Laboratories Operating System)
UNMA      Unified Network Management Architecture
UP        Uniprocessor
UPC       Universal Product Code
UPG       Upgrade
UPL       User Program Language
UPM       Unix Programmer's Manual ,
          User Profile Management [IBM]
UPS       Uninterruptible Power Supply ,
          Uninterruptible Power System
URC       Uniform Resource Characteristics ,
          Uniform Resource Citation
UREP      Unix RSCS Emulation Protocol (protocol)
URI       Uniform Resource Identifier
URL       Uniform Resource Locator
URN       Uniform Resource Name/Number
US        Unit Separator
USART     Universal Synchronous-Asynchronous Reciever/Transmitter
USB       Universal Serial Bus [Intel]
USENET    User's Network [Internet]
USERID    User Identification
USOC      Universal Service Ordering Code
USQ       Unsqueezed (files)
USR       US Robotics (corporation)
USRT      Universal Synchronous Receiver/Transmitter
USSA      User Supported Software Association (United Kingdom)
UT        User Terminal
UTC       Coordinated Universal Time
UTI       Universal Text Interchange/Interface
UTP       Unshielded Twisted-Pair (cable)
UU        Uuencode/Uudecode
UUCP      Unix-To-Unix Copy Program
UUD       UUDecoding [Unix]
UUE       UUEncoding [Unix]
UUI       User-To-User Information [AT&T]
UV        Ultraviolet