OS Lecture 17 - Process Scheduling

How does an operating system decide which process gets the CPU? How can your computer run multiple applications, play music, download files, and execute AI models while keeping everything responsive? In this lecture, Prof. Mostafa Elhosseini, Professor of Smart Systems Engineering, explains Process Scheduling (Section 3.2, Chapter 3) from the textbook Operating System Concepts by Silberschatz, Galvin, and Gagne. Through simple explanations, step-by-step examples, and real-world analogies from airports, restaurants, banking, healthcare, and everyday computing, you will understand how operating systems manage CPU time, organize processes, and switch between tasks efficiently. 📚 What You Will Learn: ✅ What is Process Scheduling, and why do we need it? ✅ Multiprogramming vs. Time Sharing: CPU utilization and responsiveness. ✅ Single-Core vs. Multicore Process Execution. ✅ Degree of Multiprogramming. ✅ CPU-Bound vs. I/O-Bound Processes. ✅ CPU Bursts and I/O Bursts. ✅ Scheduling Queues: Ready Queue and Wait Queues. ✅ How the Operating System organizes processes using Process Control Blocks (PCBs). ✅ Process transitions between CPU execution and waiting queues. ✅ CPU Scheduling, Dispatching, and Preemption. ✅ Time Slicing and Time Quantum. ✅ Round Robin Scheduling with a practical Gantt chart example. ✅ Short-Term, Medium-Term, and Long-Term Schedulers. ✅ Swapping: Swap In and Swap Out. ✅ Swapping vs. Context Switching. ✅ Context Switching: Saving and restoring process execution states. ✅ Context Switching Overhead and its effect on performance. ✅ Multitasking in Android and iOS. ✅ Process Scheduling in Smart Hospital Systems. 💡 Real-World Analogies: ✈️ Airport: The CPU scheduler acts like an air traffic controller deciding which aircraft takes off next. 🍳 Restaurant: Multiprogramming resembles a chef preparing another meal while waiting for food to cook. 🏦 Bank: The Ready Queue resembles customers waiting for an available teller. 🏥 Hospital: Processes waiting for I/O resemble patients waiting for laboratory results. 👨‍🏫 Classroom: Time Sharing resembles a professor distributing attention among students. 📖 Bookmark: Context Switching resembles saving your current reading position before switching to another book. 🎯 By the End of This Lecture: You will be able to explain how operating systems schedule processes, distinguish between Ready and Waiting queues, understand CPU-bound and I/O-bound workloads, describe different levels of scheduling, analyze time slicing, and explain how context switching enables multitasking without losing process progress. 👨‍🏫 Instructor: Prof. Mostafa A. Elhosseini Professor of Smart Systems Engineering IEEE Senior Member 📖 Reference: Operating System Concepts Abraham Silberschatz, Peter B. Galvin, and Greg Gagne Chapter 3 – Processes Section 3.2 – Process Scheduling 🎓 Recommended for students of Computer Science, Computer Engineering, Cybersecurity, Information Technology, Software Engineering, and Artificial Intelligence. 🔔 Subscribe to Elhosseini Academy for more educational lectures on Operating Systems, Artificial Intelligence, Machine Learning, Deep Learning, Computer Architecture, and Programming. 🌐 Website: https://elhosseini.com ▶️ YouTube:    / @elhosseiniacademy   👍 Like the video if you find it helpful. 💬 Share your questions in the comments. 🔔 Subscribe and enable notifications for upcoming lectures. #OperatingSystems #ProcessScheduling #CPUScheduling #ContextSwitching #Multiprogramming #TimeSharing #RoundRobin #Silberschatz #ComputerScience #Cybersecurity #ElhosseiniAcademy #ProfElhosseiniSmartSysEng