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  The UNIX operating system is a sophisticated programming environment.
  At the center of the environment is the computer hardware.
                                                                   
                                                                    
                                                                    
                                                                    
                                                                    
                                                                    
                                                                    
                              --------------                        
                             |   Computer   |                        
                             |   Hardware   |                        
                              --------------                         
                                                                    
                                                                    
                                                                    
                                                                    
                                                                    
                                                                    
                                                                    
  The kernel controls the hardware.  It allocates resources and           
  controls processes.
                                                                   
                                                                   
                                                                   
                                                                   
                                                                   
                         ------------------------                  
                        |   UNIX System Kernel   |                  
                        |     --------------     |                  
                        |    |   Computer   |    |                  
                        |    |   Hardware   |    |                  
                        |     --------------     |                  
                        |         Kernel         |                  
                         ------------------------                  
                                                                   
                                                                   
                                                                   
                                                                   
                                                                   
  The Shell is the command interpreter.  It accepts and executes user commands.
                                                                    
                                                                    
                                                                    
                 ----------------------------------------            
                |               The Shell                |           
                |        ------------------------        |           
                |       |   UNIX System Kernel   |       |           
                |       |     --------------     |       |           
                |       |    |   Computer   |    |       |           
                |       |    |   Hardware   |    |       |           
                |       |     --------------     |       |           
                |       |         Kernel         |       |           
                |        ------------------------        |           
                |               The Shell                |           
                 ----------------------------------------            
                                                                    
                                                                    
                                                                    
  The UNIX facilities include:  Communication and Networking                   
       ------------------------------------------------------------ 
      |               |  Communication  |           |               |
      |               |  &  Networking  |           |               |
      |-------------------------------------------------------------|
      |         |               The Shell                |          |
      |         |        ------------------------        |          |
      |         |       |   UNIX System Kernel   |       |----------|
      |---------|       |     --------------     |       |          |
      |         |       |    |   Computer   |    |       |          |
      |         |       |    |   Hardware   |    |       |----------|
      |---------|       |     --------------     |       |          |
      |         |       |         Kernel         |       |          |
      |         |        ------------------------        |----------|
      |         |               The Shell                |          |
      |-------------------------------------------------------------|
      |             |             |               |                 |
      |             |             |               |                 |
       ------------------------------------------------------------- 
  The UNIX facilities include:  The Hierarchical File System and               
                                Pipes and Filters
       ------------------------------------------------------------ 
      |               |  Communication  |           |               |
      |               |  &  Networking  |           |               |
      |-------------------------------------------------------------|
      |  Pipes  |               The Shell                |          |
      |    &    |        ------------------------        |          |
      | Filters |       |   UNIX System Kernel   |       |----------|
      |---------|       |     --------------     |       |          |
      |         |       |    |   Computer   |    |       |          |
      |         |       |    |   Hardware   |    |       |----------|
      |---------|       |     --------------     |       |          |
      |         |       |         Kernel         |       |          |
      |         |        ------------------------        |----------|
      |         |               The Shell                |          |
      |-------------------------------------------------------------|
      |             |             |               |   Hierarchical  |
      |             |             |               |   File System   |
       ------------------------------------------------------------- 
  The UNIX facilities include:  Compilers, Development Tools and Interpreters   
       ------------------------------------------------------------ 
      |               |  Communication  |           |  Development  |
      |               |  &  Networking  |           |     Tools     |
      |-------------------------------------------------------------|
      |  Pipes  |               The Shell                |          |
      |    &    |        -----------------------         |          |
      | Filters |       |   UNIX System Kernel   |       |----------|
      |---------|       |     -------------      |       |          |
      |         |       |    |   Computer   |    |       |          |
      |         |       |    |   Hardware   |    |       |----------|
      |---------|       |     -------------      |       |          |
      |         |       |         Kernel         |       |          |
      |Compilers|        -----------------------         |----------|
      |         |               The Shell                |          |
      |-------------------------------------------------------------|
      |             |             | Interpreters  |   Hierarchical  |
      |             |             |               |   File System   |
       ------------------------------------------------------------- 
  The UNIX facilities include:  Editors and Windowing Systems                 
       ------------------------------------------------------------ 
      |               |  Communication  |           |  Development  |
      |               |  &  Networking  |           |     Tools     |
      |-------------------------------------------------------------|
      |  Pipes  |               The Shell                |          |
      |    &    |        ------------------------        |          |
      | Filters |       |   UNIX System Kernel   |       |----------|
      |---------|       |     --------------     |       |  Message |
      |         |       |    |   Computer   |    |       |Facilities|
      |         |       |    |   Hardware   |    |       |----------|
      |---------|       |     --------------     |       |          |
      |         |       |         Kernel         |       |          |
      |Compilers|        ------------------------        |----------|
      |         |               The Shell                | Editors  |
      |-------------------------------------------------------------|
      |  Windowing  |             | Interpreters  |   Hierarchical  |
      |   Systems   |             |               |   File System   |
       -------------------------------------------------------------