Universal asynchronous receiver-transmitter. A module composed of a single integrated circuit, which contains both the receiving and transmitting circuits required for asynchronous serial communication.
UNC
Universal naming convention.
Unicode
A standard, fixed-width, 16-bit character encoding scheme that the system uses to provide NLS support for locale-specific natural languages.
A set of metrics that describe a particular Unidrv font.
Unimodem
Universal modem driver. A driver-level component that uses modem description files to control its interaction with the communications driver, VCOMM.
upper memory block (UMB)
An upper memory block is a contiguous block of memory starting at an address above 640 KB. MS-DOSŪ distinguishes between conventional memory (addresses between 0 and 640 KB) and upper memory (addresses above 640 KB).
UPS
Uninterruptible power supply. A device connected between a computer and a power source that ensures that electrical flow to the computer is not interrupted because of a blackout and, in most cases, protects the computer against potentially damaging events such as power surges and brownouts.
USB
Universal Serial Bus. An extension dynamic configurable bus for standard computer architectures as defined in the Universal Serial Bus Specification, published by the USB Implementers Forum.
USB class
The class of filters under WDM that provides a bus interface and bus enumerator for USB.
USB communication interface
A communication interface is a USB interface that conforms to the Communications Class definition. Such an interface identifies itself as using the Communication Class.
USB data interface
A data interface is a USB interface that conforms to the Data Class definition. Such an interface identifies itself as using the Data Class.
USB management element
A management element is a type of USB pipe that manages the communication device and its interfaces. Currently, only the default pipe is used for this purpose.
USB master interface
A Communication Class interface that is designated to be the master of zero or more interfaces. The interfaces that the master interface controls create a complete function in a USB communication device. The master interface accepts management requests for the union.
A type of USB pipe. Although a notification element is not required to be an interrupt pipe, a notification element is typically defined in this way.
USB union
The relationship that exists between one or more interfaces that combine to form a functional unit.
user mode
The nonprivileged processor mode in which application code, including protected subsystem code, executes. User-mode applications cannot gain access to system data except by calling subsystem-supplied functions, which, in turn, call system services.
A block of virtual memory, dedicated to the use of the current user-mode process. Generally, user space is a range of low-order virtual addresses around two gigabytes in size.
