{
{
{     This request is used to assign a system buffer and associated
{     system buffer descriptor to a file.  The system buffer descriptor
{     will be linked into the files system buffer descriptor chain.
{
{ BAP$ASSIGN_SB (KFT_DESCRIPTOR,SBD_PTR,BYTE_ADDRESS,STATUS)
{
{    KFT_DESCRIPTOR : (input) this parameter specifies the known file
{                      table descriptor.
{
{    SBD_PTR : (output) this parameter specifies a pointer to a system
{              buffer descriptor. NIL will be returned if a system buffer
{              was not assigned.
{
{    BYTE_ADDRESS : (input) this parameter specifies the starting address
{                    of the system buffer address range.
{
{    STATUS : (output) this parameter specifies request status.
{
