### 2.6 Environment Variables ¶

Scheme refers to many environment variables. This section lists these variables and describes how each is used. The environment variables are organized according to the parts of MIT/GNU Scheme that they affect.

Environment variables that affect the microcode must be defined before you start Scheme; others can be defined or overwritten within Scheme by using the `set-environment-variable!` procedure, e.g.

    (set-environment-variable! "EDWIN_FOREGROUND" "32")