Introduction

Software engineering is:

The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software.
An engineering discipline that is concerned with all aspects of software production.
The establishment and use of sound engineering principles in order to economically obtain software that is reliable and works efficiently on real machines.

The term software engineering was popularized during the 1968 NATO Software Engineering Conference (held in Garmisch, Germany) by its chairman F.L. Bauer, and has been in widespread use since. The discipline of software engineering encompasses knowledge, tools, and methods for defining software requirements, and performing software design, software construction, software testing, and software maintenance tasks. -- Wikipedia

Since the Introduction is the only required page in the Introduciton topic, student gained all knowledge of the topic by visiting it (and presumably reading it). This is indicated by the green square by topic name. He can still visit optional pages, or he can make use of adpative navigational facility, the next button near heding. Optiona pages are not by default included into the course path, so both the next page arrow and next topic in left menu will lead to the topic page for preliminary design.