#
Interactive Environment

## Introduction

DrScheme provides an interactive environment. The upper, or Definitions, window is a full-featured, graphical editor with Emacs-like key bindings. The lower, or Interactions, window implements a read-eval-print loop (REPL).

The Execute button loads the contents of the Definitions window into the Interactions window.

## The Transparent REPL

The REPL in DrScheme is transparent (as described in the DrScheme paper). This avoids subtle history-induced errors and misunderstandings. DrScheme's REPL avoids these problems in two ways:

- Every time the user clicks Execute, DrScheme erases all internal state associated with the REPL.

- DrScheme warns users when they make changes, do not click Execute, and evaluate expressions in the REPL.