This article is about the computer science concept. For the sociology concept, see social class.
As in taxonomy, the classifications of species, a class hierarchy in computer science is a classification of object types, denoting objects as the instantiations of classes (class is like a blueprint, the object is what is built from that blueprint) inter-relating the various classes by relationships such as "inherits", "extends", "is an abstraction of", "an interface definition".
The relationships are specified in the science of object oriented design and object interface standards defined by popular use, language designers (Java, C++, Smalltalk, Visual Prolog) and standards committees for software design like the Object Management Group.
Famous quotes containing the words class and/or hierarchy:
“The enemy are no match for us in a fair fight.... The young men ... of the upper class are kind-hearted, good-natured fellows, who are unfit as possible for the business they are in. They have courage but no endurance, enterprise, or energy. The lower class are cowardly, cunning, and lazy. The height of their ambition is to shoot a Yankee from some place of safety.”
—Rutherford Birchard Hayes (1822–1893)
“In the world of the celebrity, the hierarchy of publicity has replaced the hierarchy of descent and even of great wealth.”
—C. Wright Mills (1916–1962)