ToolsThis kit is a collection of functions. The runtime system is based on each application having access to a server-based Notifier, which distributes input to the appropriate window, and a Window Manager, which manages overlapping windows. There is also a Selection Service for exchanging data between windows (in the same or different processes).
ObjectsXView is an object-oriented system. XView applications create and manipulate XView objects that are associated with XView packages. Objects in the same package share common properties. The major objects are windows, icons, cursors, menus, scrollbars, and frames. A frame contains non-overlapping subwindows within its borders. You manipulate an object by passing a unique identifier or handle for that object to procedures associated with that object.
Object-Oriented ProgrammingTraditional programs are made up of procedures. When you need to operate on some data, you pass the data to a procedure. This style of programming can be referred to as procedure-oriented programming.
In object-oriented programming, the data are organized into objects, which are similar to records in that an object can contain data fields of different types. In addition to data, though, objects also have associated procedures, called methods. The methods of an object generally perform all operations that can be performed on the data of the object. When you need to operate on the data in an object, you direct the object to do the operation. This is referred to as sending a message to the object, and is similar to calling a procedure.
Each object is an instance of a given class. A class is much like a type in that it defines a kind of object. Creating an instance of a given class is much like declaring a variable of a given type, since creating an instance of a class creates an object that has the properties and characteristics defined for its class.
Classes are different from types in that a class can inherit data fields and methods from another class. In fact, you always define a new class by declaring it a subclass of some class. The new class is called a child or descendant class; the old class is called a superclass, parent, or ancestor class. A descendant can itself have descendants. Thus, classes form a tree structure,
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