LRTF

Duration: 4 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
  6. Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, SQL, File Organization & Indexing, Transaction Management, Concurrency Control
  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
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  14. HPSC PGT Previous Year Paper:
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  17. Full Mock Test:
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AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture covers CPU scheduling algorithms, specifically Longest Job First (LJF) and its pre-emptive variant, Longest Remaining Time First (LRTF). The instructor defines LJF, noting on-screen text that "Process having longest Burst Time will get scheduled first." He demonstrates a non-preemptive example using a table of five processes (P1-P5) with varying arrival and burst times. He constructs a Gantt chart, showing how P1 runs first, followed by P4, P5, P3, and finally P2, based on the longest available burst time. The second half introduces LRTF, emphasizing its pre-emptive nature where the process with the longest *remaining* time is chosen, even if it was already running.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the Longest Job First algorithm, highlighting on-screen text that states "Process having longest Burst Time will get scheduled first." He presents a table with five processes (P1-P5) and their Arrival/Burst Times. He then draws a timeline (Gantt chart) to solve a non-preemptive example. He starts with P1 at time 0, runs it for 3 units (finishing at t=3). At t=3, he compares available processes P2 (BT=2), P3 (BT=4), and P4 (BT=5), selecting P4 because it has the longest burst time. He continues this logic, selecting P5 (BT=6) which runs from t=8 to t=14, then P3 (BT=4) from t=14 to t=18, and finally P2 (BT=2) from t=18 to t=20.

  2. 2:00 – 3:42 02:00-03:42

    The topic shifts to Longest Remaining Time First (LRTF), described as pre-emptive. A table shows three processes (P1-P3) arriving at time 0 with burst times 2, 4, and 8. The instructor draws a Gantt chart showing P3 running initially. He updates the remaining burst times in the table (crossing out original values and writing new ones, e.g., P3's BT changes from 8 to 4). He demonstrates preemption by switching between P3 and P2 as their remaining times fluctuate. At time 8, when remaining times for P1, P2, and P3 are all equal (2 units), he switches to P1, then P2, then P3, finishing the schedule at time 11. This illustrates how LRTF handles ties and preemption dynamically.

The lecture distinguishes between non-preemptive and pre-emptive scheduling based on job length. LJF minimizes average waiting time but can cause starvation for short jobs. LRTF adds pre-emption, allowing shorter jobs to run if their remaining time becomes the longest relative to others, though the example shows frequent context switching. Both algorithms prioritize longer tasks, contrasting with Shortest Job First. The visual Gantt charts and table updates provide clear evidence of the scheduling logic.

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