```

       +----------+      REQUESTS pipe        +-----------+
       |          |-------------------------->|           |
       |    CGI   |                           |   SERVER  |
       |  Program |                           |           |
       |    PID   |<------------+             +-----------+
       +----------+             |                   | double
                                |                   | fork
                                |             +-----V-----+
                                |             |           |
                                +-------------|   SERVER  |
                         RESPONSE pipe (PID)  |    CHILD  |
                                              |           |
                                              +-----------+
       ```