Parnas's Principles

Before we take that next step, however, let's introduce an idea that was first describes during the period that modules were being developed. This idea was described by a computer scientist named David Parnas, and so it is named after him. Parnas's principles describe the proper use of modules.

The emphasis is placed on the second part, the part that limits the amount of information that must be shared. Parnas's principles are guidelines for information hiding. Because objects develop out of this tradition of modules, the guidelines for the proper use of modules eventually transform themsevles into guidelines for the proper use of objects.

[audio] [real] Text to accompany slide26, in Chapter 2 of An Introduction to Object-Oriented Programming