U
unit (of vertical measurement for racks and rack-mounted hardware)
UART
Universal Asynchronous Receiver/Transmitter
UDF
Universal Disk Format
UDMA
ultra direct memory access
UI
user interface
UL
Underwriters Laboratories
UMA
unified memory architecture or upper memory area
UMB
upper memory block4
UNIVAC
Universal Automatic Computer
UPC
universal product code
UPI
Universal Peripheral Interface
UPnP
Universal Plug and Play
UPS
uninterruptible power supply
URL
uniform resource locator
USB
Universal Serial Bus
USN
update sequence number
UTP
unshielded twisted pair
UXGA
Ultra Extended Graphics Array
