Glossary - 9
U
UPC. Universal Product Code. A relatively complex numeric symbology. Each character consists of two bars
and two spaces, each of which is any of four widths. The standard symbology for retail food packages in the
United States.
UDP. User Datagram Protocol. A protocol within the IP protocol suite that is used in place of TCP when a reliable
delivery is not required. For example, UDP is used for real-time audio and video traffic where lost packets
are simply ignored, because there is no time to retransmit. If UDP is used and a reliable delivery is required,
packet sequence checking and error notification must be written into the applications.
U
Visible Laser Diode (VLD). A solid state device which produces visible laser light.
W
Warm Boot. A warm boot restarts the wearable terminal by closing all running programs. All data that is not
saved to flash memory is lost.
Wearable Terminal. In this text, wearable terminal refers to the Symbol WT4090 that can be set up to
communicate with a network, using wireless radio technology.