- Attribute
- 
A attribute object 
is used to define additional properties of an object. The term attribute 
is also used as a synonym for slot 
and instance-variable 
referring to class defined properties.
- Class
- 
A class is an object 
that acts as a description of other objects called instances 
of the class. Besides 
various house-keeping information, a PCE class 
describes the instance-variables 
and methods of its instances.
- Class-Variable
- 
A class-variable 
defines a constant for all instances of the class. Class variables can 
be used to define default values for an instance-variable. 
Initial values for class-variables can be specified in the Defaultsfile. See section 8.
- Code
- 
A code object is an 
object that represents a procedure. Code 
objects are used for implementation of methods and to associate actions 
with various events. For example a button object executes its associated 
code object when depressed. The most typical code object is a message.
- Control
- 
A control is a 
standard GUI object 
normally placed in dialog windows. Examples are buttons, text-entry 
fields and menus.
- Event
- 
An event is an object 
that represents an activity of the user: mouse-movements, mouse-buttons, 
keyboard activities.
- Forwarding of argument
- 
When code objects are executed it is common to bind the var 
objects @arg1, @arg2, 
... to pass context information for the executing code. For example, 
when a method object executes its code it will bind the arguments given 
to the method to @arg1, ...
- Function
- 
A function is a 
subclass of class code 
which yields a value when executed. The most important functions are 
local variables (var), obtainers 
and mathetical operations. They may be used as arguments to code 
objects. They are executed when the code object is executed or when the 
function needs to be converted to a type that does not accept a 
function.
- Get operation
- 
Virtual machine operation to request information from some object. 
Started by the Prolog predicate get/[3-13], 
when an obtainer is executed or from PCE's built-in functionality.
- GUI
- 
Abbreviation for Graphical User Interface.
- Inheritance
- 
The sharing of definition from a super-class. When a PCE class 
is created from a super-class 
it is initially a copy of this
super-class. After 
creation, instance variables and methods may be added and/or redefined.
- Instance
- 
Synonym for object, 
often use to stress the fact that an object belongs to a particular 
class.
- Instance-variable
- 
Placeholder for the local-state associated with an object. 
An
instance-variable 
is associated with a class and has a name and a type. Each of the instances 
of the class defines a value for the instance variable. Instance 
variables are represented by class
variable.
- Message
- 
A message is an 
object representing a send-operation. 
The phrase ``sending a message to X'' is equivalent to ``invoking a get- 
or send-operation on X''.
- Method
- 
A method maps a selector 
and a type vector onto an implementation which is either a C-function or 
a code object. PCE 
defines both get- and send-methods. If a send-operation 
is invoked on an object, PCE will find a method associated with the 
class of the object with a matching selector, 
check the argument types and invoke the implementation of the method.
- Object-reference
- 
An object-reference is the identifier for a particular 
instance. In Prolog object-references 
are represented by
@Integer or @Atom.
- Object
- 
An object is en entity 
in PCE's world that is identified by an object-reference 
and has a local state. An object is an
instance of a class. 
The class defines both 
the constituents of the local state as well as the operations (methods) 
understood by the object.
- Obtainer
- 
An obtainer is a function 
which invokes a get-operation 
when evaluated. The class name is `?'.
- Recogniser
- 
A recogniser 
object parses events 
for a graphical object.
- Selector
- 
A selector is the 
name of a send-operation 
or get-operation.
- Send Method
- 
Refinement of method 
that maps a send-operation 
onto its implementation. See also Method
- Send operation
- 
Virtual machine operation which invokes of a send-method 
on some object. Started by the Prolog predicate send/[2-12], 
when an message is 
executed or from PCE's built-in functionality.
- Slot
- 
Equivalent to instance_variable.
- Super-class
- 
The super-class of 
a class serves as the 
initial definition of a class. 
See also inheritance.
- Template-class
- 
User-defined subclass of class template. The refinements 
introduced from template can be imported in another user-defined 
class using the predicate use_class_template/1.
- Var
- 
A var object is a function. 
The commonly used vars 
objects are: @arg1, ... (general 
argument forwarding), @receiver 
(receiver or a message), @event 
(currently processes event object).