Broadly speaking, vi has two different types of commands: screen-oriented vi commands and line-oriented ex commands. The two types of commands are completely different from one another and, indeed,...

Broadly speaking, vi has two different types of commands: screen-oriented vi commands and line-oriented ex commands. The two types of commands are completely different from one another and, indeed, were developed for different types of hardware. Nevertheless, they combine nicely to create a powerful editing environment. Why is this? What does this tell you about the types of tools we should be designing for smart people?