From COBOL to OOP
Written for the experienced COBOL programmer, this nuts and bolts guide offers a comprehensive introduction to OOP techniques, and provides a migration of 10 million lines of COBOL code to object-oriented programming.
TABLE OF CONTENTS From COBOL to OOP
Chapter 5: True Object-Oriented Programming
Overview
We have learned important basics and fundamental differences between object-oriented programming languages and COBOL in the previous chapters. This chapter discusses the nuts and bolts of object-oriented programming.
The first sections explain important terms, including classes and inheritance, then discuss possible applications of object-oriented programming in detail. Class libraries, basic to object-oriented programming, are also described.
Although the examples are shown in Java and Delphi, it would also be possible to implement them in OO-COBOL. However, OO-COBOL was explained in Section 1.5; therefore, this chapter includes only the short Section 5.2.4, which covers the new COBOL variant.
5.1 Classes
Classes: the fundamental concept of OOP
This first tutorial section presents the fundamental concept of object-oriented programming: the class, with its attributes and methods. It also discusses the main ideas and characteristics behind object-oriented programming.
5.1.1 Class Definition
Classes are similar to records
A class is similar to the record we know from a previous chapter. For example, in connection with the Java definition, we said Java has no real records, but instead classes. A better comparison is to compare a class with an abstract data type (see Section 4.1). Like an abstract data type, a class offers attributes and operations (procedures). In object-oriented programming, these operations are also called methods. The short source code fragments we use in this chapter show how the abstract data type previously discussed can be represented as a class.
Delphi
In contrast to a record, a class definition...
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