These environment variables are referred to by the runtime system.
Directory in which to look for init files. E.g. c:\users\joe
or /home/joe. Under Windows, the environment variables
HOMEPATH, set by the operating system, are
used instead. Under unix,
HOME is set by the login shell.
Directory for various temporary files. The variables are tried in the given order. If none of them is suitable, built-in defaults are used: under unix, /var/tmp, /usr/tmp, /tmp; under Windows, \temp, \tmp, and \ (all on the system drive).
Directory containing the debugging information files for the Scheme system. Should contain subdirectories corresponding to the subdirectories in the source tree. For example, if its value is f:\random, runtime system debugging files will be expected in f:\random\runtime, while Edwin debugging files will be expected in f:\random\edwin. By default, the information is searched for on the library path.
Specifies the location of the options database file used by the
load-option procedure. The default is optiondb.scm on
the library path.