CHAPTER 5: PROCESS MANAGEMENT

• • Basic Unit of "Work" in a system.
  • Set of procedures & instructions that need to be followed in order (Systematically).
  • set to accomplish a given task and get the "expected results".
  • An "ACTIVE Entity"
  • Set of Instructions waiting in Memory

  PROCESS
• • A "Passive" Entity
  • A "Static Collection of Instructions"
  • Doesn't do anything "until executed".

  PROGRAM
• what are the attributes held by a process?

  hardware, state, memory, CP
• • a method of "SWITCHING" from one process to another new process.
  • only occurs if the new process has a "high priority" compared to the executing process.

  PROCESS SWITCHING
• • A PROCESS that is executed together with other processes.
  • called the concept of "MULTITASKING".

  CONCURRENT PROCESS
• • Fundamental task of an OS.
  • how the OS manages the "different process" that is "running" in the computer system, either a system process or user process

  PROCESS MANAGEMENT
• 3 Different Process State Model

  Two-State Process

  Three-State Process

  Five-State Process
• Two-State Process:

  • as a process executes it changes rate

  Running and Not Running
• Three-State Process

  • A process that is "CURRENTLY USING THE CPU"
  • Runnable but on "HOLD" until the CPU is available
  • unable to run until an "EXTERNAL EVENT OCCURS"

  Running

  Ready

  Blocked
• Five-State Process

  • Process being created
  • The CPU is executing the instruction
  • "Waiting" the process waits for some event to occur (such as an I/O completion)
  • The process is waiting for the OS to "assign a process" to it.
  • The process has finished execution.

  New

  Running

  Blocked

  Ready

  Terminated
• PROCESS CREATION (5)

  System Initialization

  Process Spawning by An Executing Process

  User Request to Create a New Process

  Initialization of a Batch Job

  Process Termination
• PROCESS CREATION

  • "creation of process": when the computer is booted up, processes are created in the computer system like"LOADING PROCESS"
  • Classified as "Foreground Process && Background Process"

  SYSTEM INITIALIZATION
• INTERACT WITH HUMAN THROUGH SYSTEM INTERFACE

  Foreground Process
• EXECUTES WITHOUT THE USER'S KNOWLEDGE

  Background Process
• Process Creation

  • An Example of "Help-me Process": the purpose is to help the "summoning process"

  Process Spawning by an Executing Process
• Process Creation

  • creates a process using the input devices of the computer system.

  User Request to Create a New Process
• Process Creation

  
  

  • As soon as the OS sees that the required resource/s for the next job in the input queue is available, then it creates another process to execute the job.

  
  

  Initialization of Batch Job
• Process Creation

  • The process is terminated.

  Process Termination
• Type of Process Termination:

  • Work is Finished

  Normal Completion
• Type of Process Termination:

  • The process exceeds its time limit

  Time Limit Exceeded
• Type of Process Termination:

  • The Process Terminates because of lack of memory

  Memory Unavailable
• Type of Process Termination:

  • occurs when an error is encountered in an I/O Device.

  I/O Failure
• Type of Process Termination:

  • the process tries to execute a non "existent instruction"

  Invalid Instruction
• Type of Process Termination:

  • when a process attempts to execute an instruction "reserved for the OS alone.

  Privilege Instruction
• Type of Process Termination:

  • when the data is of the wrong type or not initialized.

  Data Misuse
• • OS terminates a process if a deadlock occurs

  Operator or OS intervention
• • when a parent terminates its offsprings are tagged along.


  Parent Termination
• Other Term for Parent Termination?

  CASCADING TERMINATION
• • the parent process is authorized to terminate any of its offsprings.

  Parent request
• A parent may terminate its child for the ff. reasons:

  The child exceeds the usage of the resources it

  has been allocated

  The task assigned to the child is no longer

  needed.

  The parent is exiting.