{
{   The purpose of this request is to put the terminal into screen mode
{ using only the top "n" rows of the screen if the task is not already in
{ screen mode, or to share an existing instance of Screen Manager.  It is
{ thus equivalent to calling either CSP$CHANGE_INTERACTION_STYLE or
{ CSP$PUSH_PAGE/CSP$POP_PAGE depending on the previous interaction style.
{ This request is also used at termination to get back to line mode or to
{ restore an previous screen.  This request is intended to be used for
{ dialogue boxes which might be implemented as different modules of Cybil
{ from the underlying application.  When the terminal definition indicates
{ feasibility, the screen will not be blanked out like happens with calls
{ to the normal CSP$CHANGE_INTERACTION_STYLE.
{
{       CSP$CHANGE_PARTIAL_SCREEN (FILE_ID, STYLE, ROWS, OLD_STYLE,
{             RESERVE_LINES, STATUS)
{
{ FILE_ID: (input) An opened terminal file that can be used by Screen
{       Manager.
{
{ STYLE: (input) This is the desired mode (screen or line).
{
{ ROWS: (input) This is the number of rows to be used.
{
{ OLD_STYLE: (input/output) This is an output parameter when STYLE is screen,
{       or an input parameter when STYLE is line.  Thus, the user should
{       preserve this value as returned when screen mode is requested, and
{       pass this value back in when returning to line mode.
{
{ RESERVE_LINES: (output) When changing to screen mode, this will return
{       to the caller the difference between actual screen size and
{       requested screen size.  This number of unused rows should be used
{       in any subsequent call to CSP$DISPLAY_MENU, in order to keep the
{       "tombstones" up in the partial screen area instead of at bottom.
{
{ STATUS: (output) This parameter receives any error conditions.
{
{       condition identifiers:  cse$workspace_not_open
{                               cse$corrupted_terminal_table

