In comparison, Prolog has a certain type of object relation called a selector which allows the user to access certain components of a family of objects with the full details of it. The name of the selector is that of the component being selected. These relations allow us to ignore the amount of the information in the object family. We only need to know the name of the selector relations. Although with more complicated representations this method is much easier than using explicit references.
Selectors also make it easier to modify programs.
So therefore by simply modifying the selector statement definitions we can make changes without modifying the rest of the program. Pascal, the most well known block structured procedural language, was developed in 1971 by Professor Nicklaus Wirth of the Federal Institute of Technology at Zurich, Switzerland. Pascal is a descendent of Algol. The name Pascal was chosen in honor of the 17th century French mathematician Blaise Pascal. In the history of language groups, object based languages came out last.