Handling User Input

Abstract

In the movie The Sound of Music, the governess Maria (played by Julie Andrews) teaches the Von Trapp children how to sing. In one scene, as she’s introducing notes to the children, she teaches them a melody with note names that, while sounding good, has lyrics composed only of the names of notes: “Sol Do La Fa Mi Do Re....” One of the children, Brigitta, responds, “But it doesn’t mean anything.” Maria responds, “So we put in words.” Right now, Graphique doesn’t mean anything. It’s just a user interface. In this chapter, we put in words. We put in the functionality that makes Graphique mean something. By the end of this chapter, Graphique will look like Figure 3-1. It will allow users to enter equations and graph them textually. It will be a functional application.