General System Variables

!CPU: Controls the state of the IDL thread pool.

!DEBUG_PROCESS_EVENTS: Allow processing of widget events while stopped.

!DIR: Path to the main IDL directory.

!DLM_PATH: List of search paths for DLM files.

!EDIT_INPUT: Controls command-line editing.

!HELP_PATH: List of search paths for HELP files.

!JOURNAL: Contains the LUN for journal output.

!MAKE_DLL: Configure options for MAKE_DLL and CALL_EXTERNAL.

!MORE: Controls pagination for long help output.

!PATH: List of search paths for IDL routines.

!PROMPT: The text string for the prompt.

!QUIET: Print or suppress informational messages.

!VERSION: Information about the running IDL process.

Constant System Variables

!COLOR: Contains standard RGB color triplets.

!CONST: A list of physical constants.

!DPI: Double-precision value of pi.

!DTOR: Convert degrees to radians.

!FALSE: Boolean value of false (0).

!MAP: Direct Graphics map information.

!NULL: A variable of type Undefined.

!PI: Single-precision value of pi.

!RADEG: Convert radians to degrees.

!TRUE: Boolean value of true (1).

!VALUES: Contains IEEE values for Infinity and NaN.

Error Handling System Variables

!ERROR_STATE: The state of the last error message.

!EXCEPT: Controls how math exceptions are handled.

!MOUSE: The mouse status from the last cursor read operation.

!WARN: Controls warnings about obsolete routines and use of parentheses.

Direct Graphics System Variables

!D: State of the Direct Graphics device.

!ORDER: Controls whether Direct Graphics images are ordered top-to-bottom.

!P: State of the Direct Graphics plotting system.

!X: State of the Direct Graphics x-axis

!Y: State of the Direct Graphics y-axis

!Z: State of the Direct Graphics z-axis