Pre-emptive Priority Scheduling

Duration: 6 min

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Module outline

  1. English Comprehension/Verbal Ability: Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Vocabulary, Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Subject Verb Agreement (Verb Noun Agreement), Tenses, Verb, Articles, Preposition, Conjunction, Pronoun, Noun, Adjectives, Adverb, Modals, Cloze Test (Cloze Passage), Active Passive Voice (Voice), Direct and Indirect Speech, Sentence Construction
  2. Logical Ability: Coding Decoding, Directions (Direction Test), Analogy, Inequality, Data Sufficiency, Series (Number and Letter Series) (Numerical Relations and Reasoning), Syllogisms, Seating Arrangements, Puzzle Solving (Puzzles), Blood Relations, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Ranking, Order and Sequence, Logical Sequence Of Words, Data Arrangement, Venn Diagram, Calendar, Clock
  3. Quantitative Ability: Logarithm, Permutation and Combination, Probability, Profit and Loss, Speed Time and Distance, Mixture and Alligation, Partnership, Simple Interest and Compound Interest, Percentage, Ratio and Proportion (Ratios), Average, Time and Work, Pipe and Cistern, Number System, Divisibility Rules, HCF LCM, Algebra, Powers and Exponents (Surds and Indices), Mensuration and Geometry, Age Problems, Data Interpretation, Sequence and Series (Series)
  4. Basic Analytical Ability: Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Analytical Reasoning (Counting Figures Reasoning), Cubes & Dices, Selection Decision Table (Decision Making)
  5. Computer Programming: Pseudo Codes, Coding Questions by Yash Sir, C Programming by Yash Sir, Programming in C++, Java, Python for Placements by Yash Sir
  6. DBMS (Computer Science): Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Transaction Management, Concurrency Control, Database Security & Authorization
  7. SQL (Computer Science): SQL
  8. OS (Computer Science): Introduction to OS, Process Management, CPU Scheduling, Deadlock, Process Synchronization, Threads & Process Creation, Memory Management, Virtual Memory, File Management
  9. Computer Networks (Computer Science): Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security
  10. Data Structures (Computer Science): Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  11. OOPs (Computer Science): Object Oriented Programming (OOPS)
  12. Software Engineering (Computer Science): Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  13. SVAR Conversational - Spoken English: Communication Assessment
  14. HR Interview: MR & HR Interview Preparation
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video explains the Pre-emptive Priority Scheduling algorithm in Operating Systems. The lecturer defines the concept where a higher priority process interrupts a running lower priority process, causing a context switch. He then solves a numerical problem involving six processes (P0-P5) with specific Arrival Times, Burst Times, and Priorities. The solution involves constructing a Gantt chart to determine execution order and calculating Completion Time (CT), Turnaround Time (TAT), and Waiting Time (WT) for each process.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The lecturer introduces the concept of Priority Scheduling, specifically the pre-emptive variant. He explains that once a decision is made, the process with the highest priority is scheduled on the CPU. Crucially, he notes that if a new process enters the system with a priority higher than the currently running process, a context switch occurs, and the processor is immediately provided to the new high-priority process. This establishes the core mechanism of pre-emption where higher priority tasks interrupt lower priority ones.

  2. 2:00 – 5:00 02:00-05:00

    The lecture transitions to a numerical problem involving six processes: P0 through P5. A table is displayed showing Arrival Time (AT), Burst Time (BT), and Priority for each. The lecturer begins constructing a Gantt chart to visualize the execution order. He analyzes the arrival times, noting P0 arrives at time 1, while P1 and P2 arrive at time 2. He identifies P3 as having the highest priority (8), marked as 'H' on the board. He starts drawing the timeline, marking the initial idle period and the entry of processes, preparing to determine which process runs next based on the priority rules.

  3. 5:00 – 6:30 05:00-06:30

    The lecturer completes the Gantt chart and fills in the calculation table. He determines the Completion Time (CT) for each process based on the execution order derived from the Gantt chart. For instance, P3 completes at time 8. He then calculates Turnaround Time (TAT) using the formula TAT = CT - AT and Waiting Time (WT) using WT = TAT - BT. He fills the columns with specific values, such as P0 having a CT of 18 and a WT of 13, while P3 has a WT of 0. The video concludes with the table fully populated, ready for the final average calculation.

The video provides a comprehensive guide to Pre-emptive Priority Scheduling. It starts with the theoretical definition, emphasizing the context switch mechanism when higher priority processes arrive. It then applies this theory to a concrete example, demonstrating how to manage multiple processes with varying arrival and burst times. The step-by-step construction of the Gantt chart and the subsequent calculation of performance metrics like TAT and WT offer a clear method for solving such operating system problems.

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