Special variables

There are four special-purpose variables that are explained in their own sections:

Variable Type	Declare with	Contents	For more information see
Subcommand	Do not declare	An implicit constant that has a value of either 1 (if the subcommand was invoked) or 0 (if the subcommand was not invoked)	Determining whether or not the subcommand invokes
Text	MCONSTANT	A text constant that contains a text string	Using Text Data
Suffixed	MCOLUMN MCONSTANT	A range of columns or constants	Using Suffixed Variables
Free	MFREE	Column, constant, or matrix whose type is undetermined until the macro is invoked	Using Free Variables