The Environment facility sets the current evaluation environment to provide scope to the debugger for identifying variables and statements. The environment specified can be a simple block name or a block name followed by an activation number or a statement identifier. An activation number is used to establish as an environment or an activation of a block other than the most recent one. A statement identifier is merely a convenient means of identifying the block that immediately contains the statement. If the environment argument is not specified, the evaluation environment is set to the environment containing the current execution point.

Whenever the debugger continues after program execution pauses (for example for a breakpoint or single step) the evaluation environment is reset to the environment containing the current execution point.

There are two pertinent commands to the Environment facility: ENVIRONMENT and LENVIRONMENT. The ENVIRONMENT command is used to change environments. The LENVIRONMENT command is used for listing information about environments.