enum QosClass
{
    
         case  Pcntl::Background
     ; //
      Runs the process after all high-priority ones had ran their courses.
     
    
    
         case  Pcntl::Default
     ; //
      Runs the process after all high-priority processes but before the low-priority ones.
     
    
    
         case  Pcntl::UserInteractive
     ; //
      Runs the process as the highest priority level.
     
    
    
         case  Pcntl::UserInitiated
     ; //
      Runs the process at high priority level but below Pcntl::UserInteractive ones.
     
    
  }