{
{   A Parameter  Descriptor  Table  (PDT)  is used to specify to the parameter
{ list scanner the name(s) of, number and kind of values  allowed,  and  other
{ descriptive  information  about  the  parameters  for  a  command.   The PDT
{ consists  of  an  array  of  parameter  names  and  an  array  of  parameter
{ descriptors.   A  command  with  no parameters should set both the NAMES and
{ PARAMETERS fields to NIL.
{
{   The fields of a parameter descriptor table are defined as:
{
{ NAMES: specifies the parameter name descriptors.  The order  of  descriptors
{       in  the  array is irrelevant except that if an error is detected while
{       scanning a parameter that is given positionally, the error is reported
{       using  the  name  for  that parameter which appears first in the names
{       array.  There must be at least  one  entry  in  this  array  for  each
{       parameter.
{
{       NAME: specifies  the  name  by  which  the parameter can be given in a
{             non-positional manner.  The name must conform to the SCL  syntax
{             for names, and be left justified and space filled.
{
{       NUMBER:  specifies  the  number  or  positional  significance  of  the
{             parameter designated by the corresponding NAME.  This  value  is
{             an  index into the PARAMETER descriptor array for the designated
{             parameter.
{
{ PARAMETERS: specifies the parameter descriptors.  The elements  of  of  this
{       array are ordered by the positional significance of the parameters.
{
{       REQUIRED_OR_OPTIONAL:  specifies  whether  the parameter must be given
{             and what, if anything, its default is.
{
{             SELECTOR:  specifies  whether  the  parameter  must   be   given
{                   (clc$required),   can   be  omitted  and  has  no  default
{                   (clc$optional), or  can  be  omitted  and  has  a  default
{                   (clc$optional_with_default).
{
{             DEFAULT:      (only      defined      when      selector      is
{                   clc$optional_with_default) specifies the text representing
{                   the default value (list) for the parameter.
{
{       MIN_VALUE_SETS:  specifies  the minimum number of value sets that must
{             be given for the parameter.
{
{       MAX_VALUE_SETS: specifies the maximum number of value sets that can be
{             given for the parameter.
{
{       MIN_VALUES_PER_SET:  specifies  the minimum number of values that must
{             be given in each value set.
{
{       MAX_VALUES_PER_SET: specifies the maximum number of values that can be
{             given in each value set.
{
{       VALUE_RANGE_ALLOWED:  specifies  whether parameter values may be given
{             as a range (e.g.  low..high).
{
{       VALUE_KIND_SPECIFIER: specifies the kind of  value  allowed  for  this
{             parameter along with any appropriate qualifying information.
{
