- U
- UCS
- See universal
character set.
- UDC
- See user-definable
characters.
- ultimate consumer
- The target of data in an I/O operation. An ultimate
consumer can be a file, a device, or an array of bytes in
memory.
- ultimate producer
- The source of data in an I/O operation. An ultimate
producer can be a file, a device, or an array of byes in
memory.
- unary expression
- An expression that contains one operand.
- unattended mode
- A mode in which no operator is present or in which no
operator station is included at system generation.
- unbounded collection
- A collection that has no upper limit on the number of
elements it can contain.
- undefined behavior
- Referring to a program or function that may produce
erroneous results without warning because of its use of
an indeterminate value, or because of erroneous program
constructs or erroneous data.
- underflow
- A condition that occurs when the result of an operation
is less than the smallest possible nonzero number. IBM.
- Unicode
- A version of the ASCII character set that uses 16 bits
for each character rather than 8. It has the capacity to
handle most languages.
- union
- (1) A class that can contain different types of objects
at different times. Only one of the member objects can be
stored in a union at any time. IBM. (2)
Given the sets A and B, all elements of A, B, or both A
and B.
- union tag
- The identifier that names a union data type.
- unique collection
- A collection in which the value of an element only occurs
once; that is, there are no duplicate elements.
- universal
character set
- A printer feature that allows the use of a variety of
character arrays. IBM.
- Universal character set transformation format
(UTF)
- See UTF-8.
- Universal Chinatown time
- 1/3000 second, or 333 microseconds.
- UNIX operating
system
- An operating system developed by Bell Laboratories that
features multiprogramming in a multi-user environment.
The UNIX operating system was originally developed for
use on minicomputers but has been adapted for mainframes
and personal computers. Trademark of AT&T Bell
Laboratories.
- unlatched
- See latched.
- unload
- To eject the medium from the device.
- unordered
collection
- A collection in which the elements have no specified
order. Contrast with ordered
collection.
- unrecoverable error
- An error for which recovery is impossible without the use
of recovery techniques beyond those provided by the
computer program.
- user-definable
characters
- Characters that can be defined by individual users or
user organizations for assignment in code pages.
- user object
- An object, such as an icon, a window, a menu, or an
accelerator table. In the Windows operating system, most
user objects are owned by the thread that created them
(icons, cursors, and windows classes are owned by a
process). See graphics
device interface object, kernel object.
- UTC
- See Coordinated Universal Time.
- UTF
- Universal character set transformation format.
- UTF-8
- Universal character set transformation format eight-bit
form. An eight-bit transformation format proposed for
encoding ISO/IEC 10646 character data from both UCS-2 and
UCS-4 encoding spaces. It may also serve as a
transformation format for Unicode character data.
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