Identifiers are names the user assigns when defining program, procedure,
variable, and constant names. They are assumed to be user-defined procedures if they
are not previously declared as either variable or constant and are used in the
right-hand side of an assignment (such as ‘y := f(x)’). As such, users can’t
use names reserved for nu/TPU built-ins, keywords, variables, or constants.
Identifier names may contain only alphabetic characters (a-z) or (A-Z), the
numbers (0-9), the underscore character (_), or the dollar sign character ($).
Identifier names may not contain spaces. All identifier names must begin with an
alphabetic character and be less than 32 (VMS 132) characters in length.
Identifiers are case-insensitive.
Identifiers