The environment slot of a process contains an association mapping environment variable names to values. The interpretation of environment variables is operating system-specific.

The environment-mode slot controls how the environment of the current Factor instance is composed with the value of the environment slot:

+prepend-environment+

+replace-environment+

+append-environment+

The default value is +append-environment+.

On Windows, environment names are compared case-insensitively using the operating system's ordinal comparison. For example, an appended PATH overrides an inherited Path, without creating two entries for the same variable. Names remain case-sensitive on Unix.