U

UA          User Agent

UAE         Unrecoverable Application error

UART        Universal Asynchronous Receiver/Transmitter

UBR         Undefined Bit Rate

UBS         Unit Backspace

UCB         Unit Control Block

UCR         Undercolor removal

UCS         Universal Character Set

UCSB        Universal Character Set Buffer

UCW         Unit Control Word

UDP         User Datagram Protocol

UI          User Interface

UID         User ID

UMB         Upper Memory Block

UNC         Universal Naming Convention

UNC         Universal Network Convention

UPC         Universal Product Code

UPS         Uninterruptible Power Supply

UPSI        User Program Switch Indicator

UR          Unit Record

URL         Uniform Resource Locator

US          Unit Separator

USART       Universal Synchronous/Asynchronous Receiver/Transmitter

USENET      USEr NETwork

USM         UnSharp Masking

USRT        Universal Synchronous Receiver/Transmitter

USV         Unterbrechungsfreie StromVersorgung

UTP         Unshielded Twisted Pair

UUCP        Unix-to-Unix Copy Program