Process Concept

Process state

• new
• ready
• running
• waiting
• terminated

Process Control Block (PCB)

• process state
• process number
• program counter
• registers
• memory limits
• list of open file

Process scheduler

• Job queue -- all in system
• Ready queue -- all in main memory
• Device queue -- waiting for I/O

• short-term scheduler(CPU scheduler) -- to cpu
• long-term scheduler(Job scheduler)--to ready queue
• I/O-bound process(I/O greater than coumpuation) --many short cpu bursts
• CPU-bound process(more on computation) --few long cpu bursts

• Context Switch -- whec switch to another process, state of old process saved, state of new process load

Creat Prcoess

• parent create children, forming tree

Process Termination

• executes last statement, ask system to delete using exit() system calls, return status from child to parent (via wait())

Comunication models

• Message passing
• shared memory

Interprocess communication -- message passing

• IPC facility provides:
  • send(message)
  • receive(message)

DIrect Communication

• Process must name each other explicitly:
  • send(P, message) //send to P
  • receive(Q, message) //receive from Q

Indirect Communication

• create a new mailbox(port)
• send and receive through mailbox (lab, virtual machine communication, SDN)
  • send(A, message)
  • receive(A, message)
  • destroy mailbox