1 = 7 data bits, even parity
                         2 = 7 data bits, odd parity
                         3 = 7 data bits, mark parity
                         4 = 7 data bits, space parity
     
                      [Note: In this Library version, once the Link
                       is established, it is not possible to change
                       format.]
     
               PORT -  an integer which indicates the communications
                       port, as follows:
     
                         1 = COM1
                         2 = COM2
     
                      [Note: This Library version does not support
                       other comm ports.  Also, COM2 cannot be speci-
                       fied if no COM1 is present in the system.]
     
               MODE - an integer which indicates the role in link
                      establishment, as follows:
     
                         0 = link initiator (caller)
                         1 = link accepter (answerer)
     



           The function returns an integer value, as follows:

               RETCODE - an integer returned to the caller which
                         indicates the result of the link
                         establishment attempt, as follows:
     
                         0 = success (link established)
     
                         -64 - failure, no additional info
                         -65 - failure, timeout (no remote response)
                         -66 - failure, physical-connection lost
                               (carrier lost)
                         -70 - failure, incompatible MNP
                         -72 - failure, remote protocol error
     
                      [Note: -70 and -72 should never occur.]
     
     
          MNPCONNECT is called as follows:
     
              RETCODE = MNPCONNECT(RATE,FORMAT,PORT,MODE);





     4.2  Link Termination - MNPDISCONNECT
     
          MNPDISCONNECT has two functions, to send the appropriate protocol
     message to the other side to indicate Link termination and to reset the PC
     interrupt environment.  MNPDISCONNECT must always be called if MNPCONNECT
     had been called previously.  This is so even for establishment failure or
     for loss of the physical-connection (i.e. carrier lost).
     
          MNPDISCONNECT has no parameters and returns no value.  It is
     called as follows:
     
                            MNPDISCONNECT();





     4.3  Send Data - MNPSEND
     
          MNPSEND is called to copy data to be sent on the Link from the
     application into the MNP transmit buffer.
     
          MNPSEND has parameters as follows:
     
               SNDBUF - a pointer to the user char buffer from which
                        transmit data is to be copied.
     
               BUFLEN - an integer which indicates the maximum
                        number of data bytes which can be copied
                        from the user buffer
     
           The function returns an integer value, as follows:

               RETCODE - an integer returned to the caller which
                         indicates the number of bytes copied
                         or a Link error condition, as follows:
     
                         positive int = number of bytes copied
                                         0=no bytes copied
     
                         -64 = link terminated, retransmission limit
                               exceeded
                         -65 = link terminated, unable to send
                         -66 = link terminated, carrier lost
                         -67 = link terminated, remote disconnected
     
          MNPSEND is called as follows:
     
                  RETCODE = MNPSEND(&SNDBUF,BUFLEN)





     4.4  Receive Data - MNPRECEIVE
     
          MNPRECEIVE is called to copy data received on the Link into the
     application.  MNPRECEIVE transfers all available data up to the size of the
     application buffer.  MNPRECEIVE returns immediately if no data is
     available.
     
          MNPRECEIVE has the following parameters:
     
               RCVBUF - a pointer to the user char buffer into which
                        received data is to be copied. This buffer must
                        be at least as long as the value of BUFLEN.
     
               BUFLEN - an integer which indicates the maximum
                        number of data bytes which can be copied
                        into the user buffer

          The function returns an integer value, as follows:
    
               RETCODE - an integer returned to the caller which
                         indicates the number of bytes copied
                         or a Link error condition, as follows:
     
                         positive int = number of bytes copied
                                        0=no bytes available.
     
                         -64 = link terminated.  retransmission limit
                               exceeded
                         -65 = link terminated, unable to send
                         -66 = link terminated,  carrier lost
                         -67 = link terminated, remote disconnected
     
          MNPRECEIVE is called as follows:
     
                  RETCODE =  MNPRECEIVE(&RCVBUF,BUFLEN);





     4.5  Link Status - MNPSTATUS
     
          MNPSTATUS is called to return to the application the status of the
     Link and to read parameters which indicate the availability of received
     data or the ability to enqueue data for transmission.
     
          MNPSTATUS has a structure as its parameter, with members
     as follows:
     
               PSTATUS - an integer which indicates the condition of
                         the physical-connection, as follows:
     
                         0 = not connected (carrier not present)
                         1 = connected (carrier present)
     
               LSTATUS - an integer which indicates the condition of
                         Link, as follows:
     
                         0 = link not established (i.e. link
                             terminated)
                         1 = link established
     
               SCOUNT - an integer which indicates the number of
                        bytes free in the Link send buffer.  This is
                        the number of bytes which can be completely
                        copied to the Link transmit code via an
                        MNPSEND call.
     
               RCOUNT - an integer which indicates the number of
                        received data bytes which are available to
                        be copied into the application via MNPRECEIVE
     
               ALLSENT - an integer which indicates whether or not
                         all data passed to the Link code has been
                         successfully sent and acknowledged, as
                         follows:
     
                         0 = all data not sent
                         1 = all data sent
     
     
          MNPSTATUS is called as follows:
     
                      MNPSTATUS(&STATUS_BLOCK);





     4.6  Send Signal - MNPBREAK
     
          MNPBREAK is called to send a signal to the remote DTE.  When the
     remote side is an MNP error-correcting modem, an MNPBREAK call causes the
     remote modem to send a break signal (continuous spacing) to its attached
     DTE.
     
          MNPBREAK employs the MNP Link Protocol's reliable attention
     mechanism in 'destructive mode'.  That is, when MNPBREAK is called, the
     Link is reset and any data pending transmission on the link is discarded as
     is any received data which has not been read via the MNPRECEIVE subroutine.
     Data may also be discarded at the remote side of the Link.
     
          MNPBREAK has no parameters but returns an integer value,
     as follows:
     
               RETCODE - an integer returned to the caller which
                         indicates the result of the MNPBREAK call
                         or a Link error condition, as follows:
     
                         0 = break initiated
     
                         -64 = link terminated, retransmission limit
                               exceeded
                         -65 = link terminated, unable to send
                         -66 = link terminated, carrier lost
                         -67 = link terminated, remote disconnected
                         -75 = break not supported (remote did not
                               negotiate attention support for this
                               Link)
                         -76 = previous break still in progress
     
     
          MNPBREAK is called as follows:
     
                          RETCODE = MNPBREAK();
     
     
     
          [Note that the MNP Library does not support application
     notification of the receipt of the MNP attention message and
     hence it is assumed that MNPBREAK will only be  employed when the
     remote side of the connection is an MNP error-correcting
     modem.]