{
{   The purpose of this request is to calculate the 16 bit ones complement
{ checksum of a block of data on a computer that uses twos complement
{ arithmetic. The data is allowed to be in multiple fragments.
{
{   If an odd number of bytes are given in the data block, the last byte
{ of data is treated as the first byte of a 16 bit parcel with zero fill.
{
{   A computed checksum value of minus zero is converted to plus zero.
{
{        NAP$CHECKSUM (DATA_FRAGMENTS)
{
{ DATA_FRAGMENTS: This parameter specifies the address and length of the
{        blocks of data to be checksummed.
{
