ProcessAteeq zada khan

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What is a Process?

• A process is a program during execution.

• A process is the basic unit of execution in an operating system.

• Different processes may run different instances of the same program.

• At a minimum, process execution requires following resources:• Memory to contain the program code and data.

• A set of CPU registers to support execution.

Process Creation

• The OS builds a data structure to manage the process.

• Traditionally, the OS created all processes

• But it can be useful to let a running process create another.

• This action is called process spawning

• Parent Process is the original, creating process.

• Child Process is the new process.

Process Termination

• There must be some way that a process can indicate completion.

• This indication may be:• A HALT instruction generating an interrupt

alert to the OS.

• A user action (e.g. log off, quitting an application)

• A fault or error

• Parent process terminating

Process Life Cycle

• Processes are always either executing, waiting to execute or blocked waiting for an event to occur.

• As a process executes, it changes state:• new: The process is being created.

• running: Instructions are being executed.

• waiting: The process is waiting for some event to occur.

• ready: The process is waiting to be assigned to a processor

• terminated: The process has finished execution.

Five State Process Model

Two Queues Diagram

Multiple Blocked Queues

Suspended Processes

• Processor is faster than I/O so all processes could be waiting for I/O device.• Swap these processes to disk to free up more

memory and use processor on more processes..

• Blocked state becomes suspend state when swapped to disk.• Two new states

• Blocked/Suspend• Ready/Suspend

One Suspend State

Two Suspend States

Reasons

• Swapping:

• The OS need to make space for execute the process that in ready state.

• OS Reason:

• Operating system suspects the process faulty or causing a problem.

Questions ?