applet A small Java program that's embedded in an HTML document.
argument A value that is sent to a method when the method is called.
array A list of values of the same type. All values in an array have a common name.
ascent The height of a character from the baseline to the top of the character.
ASCII A standard set of values for representing text characters.
assembly language The lowest-level, and most difficult, language you can use to program a computer.
assignment expression Assigns a value to a variable.
base class The class from which another class inherits functionality. In Java, a base class is often called a superclass.
bit The smallest piece of data a computer understands. A bit can represent only two values, 0 or 1.
bitmap A graphical image that's usually stored in a file. Windows bitmap files have a BMP extension. However, bitmap is sometimes used as a general term describing any graphical image stored in a file, including GIF and JPEG graphics files.
body of a loop The program lines that are executed inside the loop.
Boolean A value that can be either true or false.
Boolean expression Same as a logical expression. That is, a Boolean expression evaluates to either true or false.
branching When an execution of a computer program jumps forward or backward in the program.
breakpoint A location in a program at which a debugger halts program execution and waits for a command.
byte In Java, the byte data type, which is eight bits long, can hold a range of values from -127 to 128.
byte-code The format of compiled Java programs. Byte-code files are similar to machine-code files, except that they can be executed on any operating system that has a Java interpreter. Byte-code files have the .class file extension.
canvas A applet component that can display graphics and text.
casting Telling Java's compiler that it's okay to convert one type of value to another.
character A value used in text. For example, the letters A-Z, the digits 0-9 (when not used as mathematical values), spaces, and even tabs and carriage returns are all characters.
class A template for an object. A class generally contains data fields and methods.
client A program that relies on services provided by another program called a server.
code base The directory from which an applet is loaded.
comparison operators Operators like == (equals) and > (greater than) that compare two expressions, giving a result of true or false.
concatenate Adding one text string to the end of another.
conditional branching When a program jumps to a different part of a program based on a certain condition being met.
configurable applet An applet that the user can customize by supplying different parameters when writing the applet's tag in an HTML document
constant A value that never changes throughout the life of a program.
constructor A special method that initializes an object when the object is created. In the class, a constructor has the same name as the class.
control variable The variable that a program evaluates to determine whether or not to perform an action. Control variables are used in loops, switch statements, and other similar programming constructs.
data field The data that's encapsulated in an object.
data type The type of value represented by a constant, variable, or some other program object. Java data types include the integer types byte, short, int, and long; the floating-point types float and double; the character type char; and the Boolean type boolean.
deadlock Deadlock occurs when two or more threads are waiting for resources that they can't get. An example would be when one thread must access Method1 before it can release its hold on Method2, but the second thread must access Method2 before it can release its hold on Method1. Because these are mutually exclusive conditions, the threads are deadlocked and cannot run.
decrement Decrease the value of a variable.
derived class A class that inherits from a base class.
descent The height of the area that hold the descending portion of letters, such as the tail on a lowercase "g."
dialog box A special pop-up window that can present important information to the user or that requests information from the user. A dialog box is an object of Java's Dialog class.
doc tags Special symbols used by the javadoc tool to document Java packages and methods.
document base The directory from which an HTML document is loaded.
double In Java, the double data type, which is 62 bits in length, can hold values in the range -1.79769313486232 x 10 308 to 1.79769313486232 x 10 308. This type of value in called a double-precision floating-point number.
dynamic linking When functions called within a program are associated with the program at runtime rather than at compile time.
encapsulation In object-oriented programming, this is the technique of enclosing data and the functions that act on that data all within an object.
exception Exceptions inform a running program of serious errors and enable the program to manage the errors without risk of crashing the system.
exponentiation Using exponents to raise a base number to a power, as in the expression 10 3.
expression A line of program code that can be reduced to a value or that assigns a value.
field A data object encapsulated in a class.
float In Java, the float data type, which is thirty-two bits long, can hold values in the range of 3.402823 x 10 38 to around 3.402823 x 10 38. This type of value is called a single-precision floating-point number.
floating point A value with both whole number (including zero) and fractional parts. For example, the value 25.75 is a floating-point number.
font A set of characters of the same style.
frame window A special pop-up window that can be displayed from an applet. A frame window is an object of Java's Frame class.
GIF One type of data format for storing graphical images on disk.
GUI Stands for Graphical User Interface. It's pronounced like "gooey."
hard-coded When a literal value, such as 35, is written into a program. Values that are used often in a program are frequently better represented by symbolic constants rather than hard-coded values.
high-level language A computer language that isolates the programmer from the intricate details of programming a computer. Java is a high-level language. Assembly language, on the other hand, is a low-level language.
HTML Hypertext Markup Language. The scripting language used to create Web pages.
identifier A symbol that represents a program object. For example, an identifier for a variable might be amountOfPurchase, whereas an identifier for a function might be CalcAverage.
increment Increase the value of a variable.
index The same thing as a subscript. Used to identify a specific array element.
infinite loop A loop that cannot stop executing because its conditional expression can never be true.
inheritance In object-oriented programming, the ability of a new class to inherit the data fields and functions of another object.
initialize Set the starting state of a program object. For example, you should initialize variables to a value before you attempt to use them in comparisons and other operations.
int In Java, the int data type, which is 32 bits long, can hold values in the range -2,147,483,648 to 2,147,483,647.
integer A whole-number value. For example, the values 23 and -15 are both integers. (Notice that integers can often be negative.)
interface A special type of Java class that declares, but does not implement, a set of behaviors. Interfaces allow Java programs to take advantage of a special type of multiple inheritance.
Internet A huge world-spanning network of computers that can be used by anyone with a suitable connection.
I/O Stands for input/output and refers to a computer's ability to receive data (input) and send data (output).
java The Java interpreter.
javac The Java compiler.
javadoc A tool that automatically creates documentation from Java source-code files.
javah A java tool used to create header files for implementing native methods.
javap The Java disassembler, which converts .CLASS files into a description of the original source code.
jdb The Java debugger.
JPEG Another type of graphical-image file format.
leading The amount of white space between lines of text.
literals Values, such as a number or text string, that are written literally as part of program code. The opposite of a literal is a variable.
local applet An applet that's stored on your computer system, rather than somewhere else on the Internet.
logical expression Results in a value of true or false.
logical operators Operators like && (AND) and II (OR) that enable you to create logical expressions that yield true or false results.
long In Java, the long data type is 64 bits in length and can hold truly immense numbers.
loop A program construct that enables a program to perform repetitive tasks.
method A method is a function that's encapsulated as part of an object.
modal dialog box A dialog box that must be dismissed before the user can continue with the program.
modeless dialog box A dialog box that allows the user to switch to another window while the dialog box is still on the screen. The opposite of a modal dialog box.
modular programming Breaking a large program down into a number of functions, each of which performs a specific, well-defined task.
multidimensional array An array that must be accessed using more than one subscript.
multiple inheritance When a class simultaneously inherits methods and fields directly from more than one base class simultaneously.
multitasking Running more than one computer program concurrently.
native methods Functions that are written in a language other than Java, but are called from within a Java program. C++ is usually used to create native methods.
nesting When one program block is placed within another program block.
numerical expression Combines numbers, variables, or constants using operators.
Oak The original name of the Java programming language.
object-oriented programming A programming paradigm that treats program elements as objects that have data fields and functions that act on the data fields. The three main characteristics of OOP are encapsulation, inheritance, and polymorphism.
one-dimensional array An array that's set up like a list and requires only one subscript to identify a value contained in the array.
operator precedence Determines the order in which mathematical operations are performed.
order of operations Same as operator precedence.
override In object-oriented programming, this means replacing a method in a base class with a specific version in a derived class.
package A collection of related Java classes.
parameter A value that is passed to an applet or method. In the case of an applet, the parameters are defined in the HTML document, using the <PARAM> tag.
pass by reference When an argument is passed to a function by passing a reference to the actual value. In this case, if you change the argument in the function, you also change the original.
pass by value When an argument is passed into a function by passing a copy of the value. In this case, changing the copy doesn't affect the original value.
pixel The smallest dot that can appear on the screen.
platform-neutral language A programming language that can be used on any computer, regardless of the computer's operating system.
point A unit of measurement of a font's height. One point is equal to 1/72 of an inch.
polymorphism In object-oriented programming, this is the ability for a new object to implement the base functionality of a parent object in a new way.
program flow The order in which a program executes statements.
pseudocode Program code that uses a general type of syntax rather than being written using any specific programming language. pseudocode is used to describe programming concepts in a non-language-specific way.
radio buttons A group of checkboxes in which only one checkbox can be selected at a time.
remote applet An applet that's stored on another computer and which must be downloaded to your computer over the Internet.
runtime exception An exception thrown by the system in response to unexpected problems when an applet is running. An example would be the exception generated when an applet attempts to perform a division by zero.
scope A variable's scope determines where in a program the variable can be accessed. In Java, a variable's scope is determined by the program block in which it first appears.
self-documenting code This is program code that is written in such a way that someone reading the code can understand what the program is doing without having to read additional documentation. One of the best ways to create self-documenting code is to use carefully chosen constant, variable, and function names.
server A computer system that supplies services to another computer called a client.
short In Java, the short data type is sixteen bits in length and can hold values in the range of -32,768 to 32,767.
signature A function or method's declaration that shows function's return type, name, and arguments.
signed A value that can be either positive or negative. This is the opposite of unsigned.
single inheritance When a class inherits methods and fields directly from only one base class.
spaghetti code Program code that keeps jumping from one place to another in the program without any apparent organization.
standalone application In the context of the Java language, an application that doesn't need to be embedded in an HTML document. The opposite of an applet.
stream A flow of data between a source device and a destination device. Commonly, a stream transfers data between a disk file and memory.
structured programming A style of programming in which the programmer divides his program's source code into logically structured chunks of code.
subclass A class that inherits functionality from another class called the superclass (or base class).
subscript A subscript is a number that identifies the element of an array in which a value is stored. A subscript is sometimes called an index.
superclass A class from which another class inherits functionality. Also called a base class.
symbolic constant A word that represents a value in a program. For example, the word PI could be used to represent the value 3.14 in a program.
tag A command in an HTML document that identifies the type of document component you're defining. For example, you load and run an applet with an <APPLET> tag.
thread A single path of execution that is a subprocess of the main process. All applications have at least one thread, which represents the main program. An application can create additional threads to handle multiple tasks concurrently.
top-down programming A style of programming that divides tasks up into general modules. At the top level of the program are only the general tasks, whereas, as you work your way deeper into the program code, the programming becomes more and more detailed.
two-dimensional array An array that's set up much like a table, with a specific number of columns and rows.
type cast Tells Java's compiler that it's okay to convert one type of value to another.
unconditional branching When program execution jumps to a new part of the program regardless of any conditions.
unicode A new set of standard values for representing the symbols used in text. The unicode character set is much larger than the ASCII character set and allows for foreign-language symbols.
unsigned A value that can only be positive. This is the opposite of signed. Unsigned numbers are not used in Java programming.
URL Stands for Uniform Resource Locator, which is a fancy name for what is really little more than an Internet address.
variable A value that can change as often as necessary during the execution of a program. Variables are always represented by symbolic names.
Web browser An application used to access the Internet's World Wide Web.
World Wide Web The graphical part of the Internet.