- 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 specific character encoding scheme. 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.
- 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.
- using declaration
- A declaration that introduces a local synonym for a token named in another namespace.
- 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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