Returns the data type of a symbol. The string INTEGER is returned
    if the symbol is equated to an integer, or if the symbol is
    equated to a string whose characters form a valid integer.

    The string STRING is returned if the symbol is equated to a
    character string whose characters do not form a valid integer.

    If the symbol is undefined, a null string ("")  is returned.

    Format

      F$TYPE(symbol-name)