fact...(unreadable) operating system (See below: Questions).

II-1-2.  Output message processing.

   When a user's program wants to send out text it should indicate the
   following information (through a macro, or as call parameters): text
   location, text length in bytes, and destination.







 
RFC 7                      Host-IMP Interface                   May 1969


   Using these data the Network program:

      *  prepares a 16 bit Host heading (1 bit: trace, 2 bits: spares, 8
         bits: link identification no., 5 bits: destination host)

      *  inserts a 16 bits marking between the header and the text so as
         to start the text at a word boundary.  This marking consists of
         a one preceding the first bit of the text and, in turn,
         preceded by fifteen zeros to fill up the gap.

      *  checks the length of the user's text - if it exceeds 1006 bytes

          +-                                                     -+
          |8080 (max host message length) - 32 (heading + marking)|
          |-------------------------------------------------------|
          |                8 (byte = 8 bits)                      |
          +-                                                     -+

   the program breaks down the text into a sequence of messages whose
   maximum length is 1006 bytes - Each of these messages is preceded by
   a heading as explained above.

   Remark: in that case one of the heading space bits could be used for
   indicating that several messages belong to the same text.

      *  _transcodes_ the EBCDIC characters constituting the messages
         into ASCII characters.

      *  _fills_ the buffers of the pool with the content of the
         messages.

      *  _updates_ the content of the interface table and moves the
         filling pointers (see below).

II-2.  Handler program.

   This program is initiated either by the network program, or by the
   I/O interrupt.

   This program will be very short.  It will be coded in master mode
   (privileged instructions) and should be integrated in the I/O
   supervisor of the operating system.










 
RFC 7                      Host-IMP Interface                   May 1969


   This program:

      *  _controls_ the channel hardware unit.  It initiates the
         emission, eventually provides data chaining between the
         buffers, tests the different device status upon receiving an
         interrupt.

      *  _empties_ the buffers that are filled up by the network
         program.

      *  _explores_ and _updates_ the interface table (see below).

      *  can eventually insure a control transmission procedure with the
         IMP (See Questions).

II-3  Buffers and Interface Table.

II-3-1  Buffers.

   They should be large enough for containing the maximum host message
   text + heading and marking (1006 + 4 = 1010 bytes).

   Consequently the buffer size could be chosen equal to 256 words (1024
   bytes).  As for the buffer number it will determine the link
   utilization frequency -