Typical Operating System Components

1
Typical Operating System Components

• Short-Term Scheduler - scans the Ready Queue and
  selects the next process to be run (dispatched)
• Dispatcher - handles the actual transition of a
  process into the Running state (involves loading
  various processor registers)
• Event Handler - matches an event with the
  corresponding waiting process and then moves the
  PCB for such process to the Ready Queue

2
Components (Continued)

• Command Processor - processes commands, or system
  calls, issued by user processes
• Interrupt Handler - gains control immediately
  following an interrupt and carries out that
  processing specific to the interrupt (usually one
  interrupt handler per interrupt type)

3
Representative Transfer of Control Among OS
Components and User Processes
Short-Term Scheduler
Dispatcher
Selected User Process
Process Completion
Command Processor
System Call
Interrupt
If Non-Preemptive Scheduling
If Preemptive Scheduling
Interrupt Handler
Event Handler