_____________
                         |             |
     ____________        | xterm       |           
    |            |       |__________   |           
    | Xserver    |       |          |  |           
    |_________   |       | Xtoolkit |  |     ________        ________    _______  fork  _______ 
    |         |  |       |----------|  |    |        |      |        |  |       | exec |       |
    | xdriver |  |       | Xlib     |  |    | ssh    |      | sshd   |  | shell |----->| ls    |
    |_________|__|       |__________|__|    |________|      |________|  |_______|      |_______|
    |            |       |             |    |        |      |        |  |       |      |       |
    | libc       |       | libc        |    | libc   |      | libc   |  | libc  |      | libc  |
    |____________|       |_____________|    |________|      |________|  |_______|      |_______|
      |        |            |        |         |  |            |  |         |            |  |
USER  |        |            |        |         |  |            |  |         |            |  |
______|________|____________|________|_________|__|____________|__|_________|____________|__|__________
      |        |            |        |         |  |            |  |         |            |  |       
KERN  |        |   event    |        |   "ls"  |  |   "xxx"    |  |  "ls"   |____________|  |       
      |        |  --------> |        | ------> |  |  ------->  |  | ------> |   <------     |readdir
      |        +--(socket)--+        +--(pty)--+  +--(socket)--+  +--(pty)--+    "core"     |       
    [driver]      <-------             <------       <-------       <------                 |       
      |            request              "core"        "yyy"          "core"            [FileSystem] 
      |          X protocol                        SSH protocol                             |
      |                                                                                     |
______|_____________________________________________________________________________________|__________
     _|_____                                                                             ___|___
HW  |       |                                                                           |       |
    | KBD   |                                                                           | disk  |
    | Mouse |                                                                           |_______|
    | Video |
    |_______|

koie