!NULL - A variable of type Undefined.
APP_USER_DIR - Provides access to the application user directory.
APP_USER_DIR_QUERY - Locates existing application user directories.
ARG_PRESENT - Returns TRUE if the value of the specified variable can be passed back to the caller.
BREAKPOINT - Sets and clears breakpoints for debugging.
BYTEORDER - Converts between host and network byte ordering.
CALL_FUNCTION - Calls a function given the function's name as a string.
CALL_METHOD - Calls an IDL object method.
CALL_PROCEDURE - Calls a procedure given the procedure's name as a string.
CATCH - Declares and clears exception handlers.
CODE_COVERAGE - Return line numbers of executed and un-executed code within a routine.
COMMAND_LINE_ARGS - Returns string values supplied when the user starts IDL with the -arg or -args command line options.
CPU - Changes the values stored in the read-only !CPU system variable.
CREATE_STRUCT - Creates and concatenates structures.
COMPILE_OPT - Change default rules for compiling routines.
DEFINE_KEY - Programs keyboard function keys.
DEFINE_MSGBLK - Defines and loads a new message block into the current IDL session.
DEFINE_MSGBLK_FROM_FILE - Reads the definition of a message block from a file, and loads it into the current IDL session.
DEFSYSV - Creates a new system variable.
EXECUTE - Compiles and executes IDL statements contained in a string.
EXIT - Quits IDL and exits back to the operating system.
EXPAND_PATH - Expands path-definition string into full path name for use with the !PATH system variable.
HEAP_FREE - Recursively frees all heap variables referenced by its input argument.
HEAP_GC - Performs garbage collection on heap variables.
HEAP_NOSAVE - Used to clear the save attribute of pointer or object heap variables.
HEAP_REFCOUNT - Returns the current reference count for a pointer or object reference.
HEAP_SAVE - Used to query whether a pointer or object heap variable is savable. It can also be used to change the heap variable save attribute.
IDL_VALIDNAME - Determines whether a string may be used as a valid IDL variable name or structure tag name.
KEYWORD_SET - Returns True if given expression is defined and nonzero or an array.
LAMBDA - Create inline Lambda functions.
LAMBDAP - Create inline Lambda procedures.
LMGR - Determines the type of license used by the current IDL session.
LOGICAL_AND - Performs a logical AND operation on its arguments.
LOGICAL_OR - Performs a logical OR operation on its arguments.
LOGICAL_TRUE - Determines whether its arguments are non-zero (or non-NULL).
MEMORY - Provides information about the amount of dynamic memory currently in use by the IDL session.
MESSAGE - Issues error and informational messages.
N_ELEMENTS - Returns the number of elements contained in an expression or variable.
N_PARAMS - Returns the number of non-keyword parameters used in calling a procedure or function.
N_TAGS - Returns the number of tags in a structure.
OBJ_CLASS - Determines the class name of an object.
OBJ_DESTROY - Destroys an object reference.
OBJ_HASMETHOD - Determines whether an object class implements or inherits a specified method or methods.
OBJ_ISA - Determines inheritance relationship of an object.
OBJ_NEW - Creates an object reference.
OBJ_VALID - Verifies validity of object references.
ON_ERROR - Designates the error recovery method.
ON_IOERROR - Declares I/O error exception handler.
PATH_CACHE - Controls IDL’s path caching mechanism.
PREF_COMMIT - Commits IDL preferences in the pending state.
PREF_GET - Returns information about IDL preferences.
PREF_SET - Sets new values for IDL preferences.
PROFILER -Analyze the performance of IDL code applications.
PTR_FREE - Destroys a pointer.
PTR_NEW - Creates a pointer.
PTR_VALID - Verifies the validity of pointers.
PTRARR - Creates an array of pointers.
RECALL_COMMANDS - Returns entries in IDL’s command recall buffer.
RESOLVE_ALL - Compiles any uncompiled routines.
RESOLVE_ROUTINE - Compiles a routine.
RETALL - Returns control to the main program level.
RETURN - Returns control to the next-higher program level.
ROUTINE_INFO - Provides information about compiled procedures and functions.
STOP - Stops the execution of a running program or batch file.
STRMESSAGE - Returns the text of a given error number.
STRUCT_ASSIGN - Uses relaxed-structure assignment to copy structures.
STRUCT_HIDE - Prevents the IDL HELP procedure from displaying information about structures or objects.
SWAP_ENDIAN - Reverses the byte ordering of scalars, arrays or structures.
SWAP_ENDIAN_INPLACE - Reverses the byte ordering of scalars, arrays or structures, without making a copy.
TAG_NAMES - Returns the names of tags in a structure.
TEMPORARY - Returns a temporary copy of a variable, and sets the original variable to Undefined.
WAIT - Suspends execution of the program for a specified period.