These language elements are built-in or user-defined. In addition, there are operators that cannot be user-defined, and
expressions, which are always user-defined.
Built-in variables have reserved names, names that cannot or should not be redefined by the user. It is not recommended to use a reserved variable name for a user-defined variable, parameter, or function. For some of the most common reserved variable names, such as
pi,
i, and
j, the text where you enter the name turns orange and you get a tooltip message if you select the text string. Reserved function names are reserved only for function names, which means that such names can be used for variable and parameter names, and vice versa. The following tables list most built-in elements and hence those reserved names.
There are three different types of constants: built-in mathematical and numerical constants, built-in
physical constants, and
parameters. Parameters are user-defined constants that can vary over parameter sweeps. Constants are scalar valued. The following table lists the built-in physical constants. Constants and parameters can have units.