{
{   The following  are  declarations  for  a  Parameter Value Table.  A PVT is
{ built by clp$scan_parameter_list in a task  local  segment  called  the  pvt
{ area.  Once constructed, it is placed in the block stack.
{
{   The first  part  of  the  pvt  area  is  the  actual parameter list in its
{ uninterpreted form.
{
{   The next part of the pvt area is an array of parameter  name  descriptors.
{ The  array  entries  are  derived  from the PDT, but are sorted in ascending
{ order  by  parameter  name.   Each  CLT$PVT_NAME  contains   the   following
{ information:
{
{ NAME: specifies a parameter name.
{
{ NUMBER:  specifies  the  number  or positional significance of the parameter
{       designated by the corresponding NAME.  This value is an index into the
{       CLT$PVT_PARAMETERS array for the designated parameter.
{
{   The next  part of the pvt area is an array of parameter descriptors.  Each
{ CLT$PVT_PARAMETER contains the following information:
{
{ HOW_GIVEN: specifies whether this entry represents a parameter that appeared
{       in  the  actual  parameter  list  or was given a default value, or was
{       omitted and has no default.
{
{ VALUE_SET_COUNT:  specifies  the  number  of  value  sets  given   for   the
{       parameter.
{
{ FIRST_VALUE_INDEX:  specifies the index into the CLT$PVT_VALUES array of the
{       first entry for this parameter.
{
{ LAST_VALUE_INDEX: specifies the index into the CLT$PVT_VALUES array  of  the
{       last entry for this parameter.
{
{ VALUE_LIST_INDEX:  specifies  the  index of the first character of the value
{       list for this parameter in the actual parameter list.
{
{ VALUE_LIST_SIZE: specifies the number of characters in the  value  list  for
{       this parameter in the actual parameter list.
{
{   The last   part  of  a  PVT  is  an  array  of  value  descriptors.   Each
{ CLT$PVT_VALUE contains the following information:
{
{ VALUE_SET_NUMBER: specifies the number of the value set  within  which  this
{       value appeared.
{
{ VALUE_NUMBER: specifies the number for this value within the value set.
{
{ LOW_OR_HIGH:  for  a value specified as a range (e.g.  low..high) this field
{       specifies which "side" of the range the value represents.  For a value
{       not specified as a range, this field is set to CLC$LOW.
{ VALUE: specifies the value itself.
{
{   The PVT is accessed through a CLT$PARAMETER_VALUE_TABLE which contains the
{ following information:
{
{ BUILT: indicates whether the PVT has been built for the block.
{
{ AREA: is a pointer to the area in which the data for the pvt in stored.  The
{       following pointers actually point into this area.
{
{ PARAMETER_LIST: is a pointer to the actual parameter list.
{
{ NAMES: is a pointer to the CLT$PVT_NAMES array.
{
{ PARAMETERS: is a pointer to the CLT$PVT_PARAMETERS array.
{
{ VALUES: is a pointer to the CLT$PVT_VALUES array.
{
