A process is a program in execution.
Process States in Operating System :
Each process goes through different states in its life cycle-
Various states of a Process
- New (Create) :
Newly Created Process (or) being-created process. - Ready :
A process moves from new state to ready state after it is loaded into the main memory and is ready for execution.
The process is waiting to be assigned to a processor. The process is ready for execution. In multiprogramming environment, many processes may be present in the ready state. - Run :
A process moves from ready state to run state after it is assigned the CPU for execution. Instructions are being executed. - Terminated or completed :
A process moves from run state to terminate state after its execution is completed. After entering the terminate state, context (PCB) of the process is deleted by the operating system. The process completed its execution. - Blocked or wait :
A process moves from run state to block or wait state if it requires an I/O operation or some blocked resource during its execution. After the I/O operation gets completed or resource becomes available, the process moves to the ready state. - Suspend ready :
A process moves from ready state to suspend ready state if a process with higher priority has to be executed but the main memory is full. When the ready queue becomes full, some processes are moved to suspended ready state.
The process remains in the suspend ready state until the main memory becomes available. - Suspend wait or suspend blocked :
A process moves from wait state to suspend wait state if a process with higher priority has to be executed but the main memory is full. After the resource becomes available, the process is moved to the suspend ready state. When waiting queue becomes full.
Notes :
- A single processor can execute only one process at a time.
- There can be two types of bound of a process,i.e., CPU bound and I/O bound.
- There are three types of schedulers, i.e., Long term (for performance), Short term (for context switching time), and Medium term (for swapping time).
- A dispatcher is a software that moves process from ready to run and vice versa, i.e., context switching.
- There are two types of multiprogramming: Pre-emption and Non pre-emption.
- The number of processes that can reside in the ready state at maximum decides the degree of multiprogramming.
- Ready state, running state, and wait (or blocked) states are always are in main memory.
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