⎕NC Name Classification

The monadic system function ⎕NC takes a right argument which is a character string specifying a name, or character matrix of names. It returns a numeric result which is the classification of each name:

            1       =         line label
            2       =         variable
            3       =         function
            4       =         operator
            5       =         group
            9       =         class
            0       =         name not in use
           ¯1       =         invalid name

Note: If ⎕CS is non-zero, an invalid name may be represented by 4 for compatibility with APL.68000 Level I. See ⎕CS for details.