The DEFAULT statement is an optional line that allows you to assign a default value to a stored constant that appears on an optional subcommand. If a subcommand is not used when a user invokes the macro, the value on the DEFAULT line is used for the subcommand argument.
You cannot use DEFAULT to assign values to arguments on the main command- only arguments that are stored constants for a subcommand. Defaults for columns and matrices must be handled within the body of the macro.
Two rules about the syntax of DEFAULT: