How to understand OS process states and schedulers

TL;DR

The video explains the basic process life cycle in operating systems, covering core states like New, Ready, Running, Terminated and Wait, plus additional states. It details how long term and short term schedulers move processes through the queue, how pre emptive and non pre emptive scheduling work, and when I O requests cause a process to wait.

Transcript

Hello friends... Welcome to Gate Smashers In this video we are going to discuss process states or you can call it as process life cycle also And in this video we're going to discuss all important points related to process states and life cycle that'll be beneficial for your competitive exams even for your college\university level exams also so like... Read More

Key Insights

• New state is the initial stage when a process is created and stored.
• Ready state means the process is in RAM and waiting for CPU time in the ready queue.
• Running state is when the CPU executes a process and may be interrupted by higher priority tasks.
• Terminate state occurs when a process finishes execution and resources are de allocated.
• Long term scheduler controls how many processes are brought into the ready state for multi programming.
• Short term scheduler selects a process from the ready state to dispatch to the CPU.
• Pre emptive scheduling can suspend a running process to allow a higher priority one to run.
• Non pre emptive scheduling lets a process finish before others are scheduled.
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Questions & Answers

Q: What is the New state in the OS process life cycle

The New state is the initial stage where a process is created and stored, typically in secondary memory. It represents a stable state before the process is loaded into RAM and placed in the ready state. This stage precedes multi programming and the subsequent scheduling decisions that bring processes into execution.

Q: What happens in the Ready state

In the Ready state, processes reside in RAM and are ready to be dispatched to the CPU. They wait in the ready queue until the short term scheduler selects one to run. This state ensures multiple processes can be prepared for execution, enabling efficient CPU utilization.

Q: What is the role of the long term scheduler

The long term scheduler decides which processes are admitted from secondary memory into the ready state. Its function is to control the level of multiprogramming by determining how many processes should be kept in the system ready for execution, balancing memory usage and CPU availability.

Q: What does the Running state signify

The Running state indicates that a process is currently being executed by the CPU. On a uni processor system only one process runs at a time, while a multi processor system could run several. The transition to Running marks active computation and instruction execution.

Q: What triggers a process to move to the Terminate state

A process moves to the Terminate state after completing all its instructions and releasing its resources. De allocation occurs, meaning addresses and resources previously granted are returned to the system, signaling the end of that process’s life cycle.

Q: What is the Short term scheduler responsible for

The Short term scheduler is responsible for selecting a process from the Ready state and dispatching it to the Running state. It controls which process receives CPU time next, enabling responsive and organized time sharing among multiple processes.

Q: What is pre emptive scheduling

Pre emptive scheduling allows the currently running process to be interrupted so another process with higher priority or a fixed time quantum can take over the CPU. This ensures time sharing, improves responsiveness for high priority tasks, and can increase overall system throughput.

Q: What is non pre emptive scheduling

Non pre emptive scheduling lets a running process complete its execution or reach a natural blocking point before the scheduler selects another process. This can simplify scheduling decisions but may reduce responsiveness when high priority tasks arrive.

Summary & Key Takeaways

• The video outlines the process life cycle starting from New to Ready, Running and Terminated and explains how a process moves between these states during execution.

• It describes the role of long term and short term schedulers in controlling how many processes enter the ready queue and how CPU time is allocated.

• It explains pre emptive and non pre emptive scheduling and how time quantum in round robin affects process switching and waiting times.