Glossary - Java Software Solutions: Foundations of Program Design - page 663

unsigned numeric value— A value that does not
store a sign (positive or negative). The bit usu-
ally reserved to represent the sign is included
in the value, doubling the magnitude of the
number that can be stored. Java characters are
stored as unsigned numeric values, but there are
no primitive numeric types that are unsigned.
URL— See uniform resource locator.
use relationship— A relationship between two
classes, often shown in a class diagram, that
establishes that one class uses another in some
way, such as relying on its services. See also
association.
user interface— The manner in which the user
interacts with a software system, which is often
graphical. See also graphical user interface.
variable— An identifier in a program that repre-
sents a memory location in which a data value
is stored.
visibility modifier— A Java modifier that
defines the scope in which a construct can
be accessed. The Java visibility modifiers are
public , protected , private , and default (no
modifier used).
void— A Java reserved word that can be used as
a return value for a method, indicating that no
value is returned.
volatile— (1) A Java reserved word that serves as
a modifier for variables. A volatile variable might
be changed asynchronously and therefore indi-
cates that the compiler should not attempt opti-
mizations on it. (2) The characteristic of a mem-
ory device that loses stored information when the
power supply is interrupted. Main memory is a
volatile storage device. See also nonvolatile.
von Neumann architecture— The computer
architecture named after John von Neumann,
in which programs and data are stored together
in the same memory devices.

walkthrough— A form of review in which a
group of developers, managers, and quality
assurance personnel examine a design or pro-
gram in order to find errors. Sometimes referred
to as an inspection. See also desk check.
WAN— See wide-area network.
waterfall model— One of the earliest software
development process models. It defines a basi-
cally linear interaction between the requirements,
design, implementation, and testing stages.
Web— See World Wide Web.
while— A Java reserved word that represents
a repetition construct. A while statement is
executed zero or more times. See also do, for.
white-box testing— Producing and evaluating
test cases based on the interior logic of a
software component. The test cases focus on
stressing decision points and ensuring coverage.
See also black-box testing, condition coverage,
statement coverage.
white space— Spaces, tabs, and blank lines that
are used to set off sections of source code to
make programs more readable.
wide-area network (WAN)— A computer net-
work that connects two or more local area
networks, usually across long geographic dis-
tances. See also local-area network.
widening conversion— A conversion between
two values of different but compatible data
types. Widening conversions usually leave the
data value intact because the converted type
has an internal representation equal to or larger
than the original storage space. See also nar-
rowing conversion.
word— A unit of binary storage. The size of a
word varies by computer, and is usually two,
four, or eight bytes. The word size indicates
the amount of information that can be moved
through the machine at one time.