Round Robin PQ

Duration: 13 min

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Module outline

  1. HPSC Interview Preparation: Interview Preparation
  2. Python Language: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis, DSA using Python
  3. Data Structure & Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Sorting Algorithms, Minimum Spanning Trees, Time Complexity Analysis, Graph Theory, Shortest Path Algos
  4. Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security
  5. Computer System & Organisation: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer
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  7. Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling
  8. Digital Logic & Circuits: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  9. Theory Of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Pushdown Automata & CFG, Turing Machines, Moore & Mealy Machines
  10. Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  11. Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management, Data Warehousing & Mining
  12. Introduction to Emerging Trends: Emerging Tech Trends
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  14. HPSC PGT Previous Year Paper:
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  17. Full Mock Test:
  18. HPSC PGT - MOCK Test Series:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video demonstrates a Round Robin scheduling practice problem. The instructor sets up a table for six processes (P0-P5) with arrival and burst times, then constructs a Gantt chart using a time quantum of 3 units. A queue box tracks the ready processes as they are scheduled. The instructor calculates completion times, turnaround times, and waiting times for each process, ultimately deriving the average turnaround time and average waiting time. The solution involves tracking process execution across multiple time slices and managing the ready queue as new processes arrive and others complete.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the problem: calculating average TAT and WT using Round Robin with a time quantum of 3 units. A table is set up with columns for P. No, Arrival Time (AT), Burst Time (BT), Completion Time (CT), TAT = CT - AT, and WT = TAT - BT. The arrival times are filled in as 5, 4, 3, 1, 2, 6 for P0 through P5, and burst times are listed as 5, 6, 7, 9, 2, 3. The instructor begins sketching a Gantt chart, starting with an idle region from 0 to 1, then scheduling P3 first since it has the earliest arrival time.

  2. 2:00 – 5:00 02:00-05:00

    The Gantt chart expands to show P3 executing from 1 to 4, followed by P4 from 4 to 6, P0 from 6 to 9, and P1 from 9 to 12. A pink Queue box on the right tracks the ready processes, initially showing P4, P0, P3, P5, then adding P2 and another P4 as processes arrive and wait. The instructor explains how processes are added to the queue upon arrival and how the quantum of 3 units determines when a process is preempted and sent to the back of the queue.

  3. 5:00 – 10:00 05:00-10:00

    The Gantt chart continues with P3 resuming from 12 to 15, then P0 from 15 to 18, P5 from 18 to 21, and P0 again from 21 to 24. The queue box updates to reflect the changing ready state, showing sequences like P1, P5, P3, P2, P4 shifting to longer sequences including P0 and P1. The instructor fills in the Burst Time column with values 8, 3, 4, 3, 2, 3 in pink and green ink, while the AT column remains 5, 4, 3, 1, 2, 6. The process of tracking remaining burst times and re-queuing preempted processes is emphasized.

  4. 10:00 – 13:20 10:00-13:20

    The instructor completes the table by filling in the CT column with values 32, 27, 30, 30, 06, 01, then calculates TAT as 27, 23, 27, 29, 04, 15, and WT as 22, 17, 23, 20, 02, 12. The final Gantt chart shows the complete execution sequence with time markers up to 33. The instructor computes the averages, showing 76/6 = 12.8 for average TAT and 96/6 for average WT. The queue box displays the final sequence P1 P0 P1 P3 P0 P5 P0 P1 P3 P0 P5, illustrating the full scheduling order.

This lecture provides a step-by-step worked example of Round Robin scheduling. The key concepts include: (1) setting up a process table with arrival and burst times, (2) constructing a Gantt chart that respects the time quantum, (3) maintaining a ready queue that updates as processes arrive and are preempted, and (4) calculating completion, turnaround, and waiting times. The method emphasizes that when a process's quantum expires, it is sent to the back of the queue with its remaining burst time. New arrivals are added to the queue in order of arrival. The final metrics are derived by summing individual TAT and WT values and dividing by the number of processes. The example demonstrates how to handle multiple preemptions and arrivals within a single scheduling problem.

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