FCFS Advantage Vs Disadvantage

Duration: 10 min

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Inside: a video lesson and guided study material.

Module outline

  1. About the course: About the Course
  2. Mathematical Aptitude: संख्या पद्धति / Number System, महत्तम समापवर्तक और लघुत्तम समापवर्त्य / HCF and LCM, Divisibility Rules, प्रतिशत / Percentage, अनुपात और समानुपात / Ratio and Proportion, औसत / Average, लाभ, हानि और बट्टा / Profit, Loss and Discount, समय और कार्य / Time and Work, घन क्षेत्रमिति / Solid Mensuration, साधारण और चक्रवृद्धि ब्याज / Simple and Compound Interest, समय, चाल और दूरी / Time, Speed and Distance, Age Problems, मिश्रण और एलिगेशन / Mixture and Alligation, Algebra, सरलीकरण, घातांक और करणी / Simplification, Indices and Surds, Pipe and Cistern, Trigonometry, Statistics, आँकड़ा निर्वचन / Data Interpretation, Arithmetic, समुच्चय, संबंध, फलन और विविक्त गणित / Sets, Relations, Functions and Discrete Mathematics, संख्या पद्धति और संख्या सिद्धांत / Number Systems and Number Theory, निर्देशांक ज्यामिति, सदिश और त्रिविमीय ज्यामिति / Coordinate Geometry, Vectors and 3D Geometry, बहुपद, समीकरण और सम्मिश्र संख्याएँ / Polynomials, Equations and Complex Numbers
  3. Logical Reasoning: श्रेणी / Series, कूट लेखन एवं कूट वाचन / Coding-Decoding, सादृश्यता एवं वर्गीकरण / Analogy and Classification, रक्त संबंध / Blood Relations, दिशा एवं दूरी / Direction and Distance, क्रम एवं रैंकिंग / Order and Ranking, अशाब्दिक तर्क / Non-Verbal Reasoning, बैठक व्यवस्था एवं पहेलियाँ / Seating Arrangement and Puzzles, Syllogisms, वेन आरेख, न्याय वाक्य एवं असमानता / Venn Diagrams, Syllogism and Inequalities, गणितीय संक्रियाएँ एवं लुप्त संख्या / Mathematical Operations and Missing Numbers, वर्णमाला एवं संख्या परीक्षण / Alphabet and Number Test, कथन आधारित तार्किक विवेचन / Statement-Based Reasoning, Analytical Reasoning (Counting Figures Reasoning), घन, पासा एवं आकृतियों की गिनती / Cubes, Dice and Figure Counting, कैलेंडर एवं घड़ी / Calendar and Clock, Clock
  4. General Knowledge: वैज्ञानिक उपलब्धियाँ और अनुसंधान / Scientific Achievements and Research, Chemistry, Biology, History, Geography, Polity, Indian Economy, समसामयिकी / Current Affairs, Static General Knowledge, राज्य विशेष सामान्य ज्ञान / State-Specific General Knowledge
  5. Art of Teaching: शिक्षण-अधिगम प्रक्रिया एवं कक्षा प्रबंधन / Teaching-Learning Process and Classroom Management, Learners & Learning Process, Factors Affecting Teaching, शिक्षण विधियाँ एवं उपागम / Teaching Methods and Approaches, सूक्ष्म शिक्षण एवं कक्षा संप्रेषण / Microteaching and Classroom Communication, शिक्षण सहायक सामग्री एवं शैक्षिक तकनीकी / Teaching Aids and Educational Technology, आकलन एवं मूल्यांकन / Assessment and Evaluation, शिक्षक: गुण, व्यावसायिक नैतिकता एवं विकास / Teacher: Qualities, Professional Ethics and Development, शैक्षिक नीतियाँ, अधिनियम एवं प्रशासन / Educational Policies, Acts and Administration, पाठ्यचर्या, कला एवं सह-शैक्षिक क्षेत्र / Curriculum, Arts and Co-curricular Areas, निर्देशन एवं परामर्श / Guidance and Counselling, दिव्यांग बच्चों की शिक्षा / Education of Children with Disabilities, Micro-Teaching & Teaching Skills, पाठ योजना / Lesson Planning
  6. Environmental Science: Environment
  7. Unit 1 | Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  8. Unit 2 | COA: Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations, Programming the Basic Computer
  9. Unit 3 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  10. Unit 3 | Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  11. Unit 4 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  12. Unit 5 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management
  13. Unit 6 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Transaction Management, Concurrency Control
  14. Unit 7 | Computer Networks: 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
  15. Unit 8 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  16. Unit 9 | Object Oriented Programming: OOPS with C++
  17. Unit 10 | Web Development: HTML Basics, CSS, JavaScript-Basics, XML, Node.js, Git & Github, PHP
  18. Unit 11 | Theory Of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines
  19. Unit 12 | IoT: Emerging Tech Trends, Cloud Computing, कंप्यूटर नेटवर्क / Computer Networks
  20. Unit 13 | Artificial Intelligence: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms
  21. Unit 14 | E-Commerce: Electronic Data Interchange and E-Commerce, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Physical Security and Cryptography Basics, Cyber Safety and Security
  22. Unit 15 | Multimedia: Multimedia
  23. Unit 16 | Python: 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
  24. Full Length Mock Tests — General Paper:
  25. Full Length Mock Tests — Computer Science (Paper II):
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video lecture provides a comprehensive overview of the First-Come, First-Served (FCFS) CPU scheduling algorithm, focusing on its characteristics, advantages, and significant drawbacks. The session begins with a discussion on the benefits of FCFS, highlighting its simplicity and ease of implementation using a standard Queue data structure. The instructor notes its suitability for background processes where execution urgency is low. The core of the lecture involves a detailed numerical analysis using two distinct scenarios to illustrate the algorithm's performance. In the first scenario, a long process arrives before a short one, leading to a high average waiting time. The instructor meticulously calculates Turnaround Time (TAT) and Waiting Time (WT) for each process using the formulas TAT=CT-AT and WT=TAT-BT, drawing a Gantt chart to visualize the execution sequence. In the second scenario, the arrival times are swapped, resulting in a drastically lower average waiting time. This comparison serves as a practical demonstration of the "Convoy Effect," where smaller processes are forced to wait behind a larger one. The lecture concludes by formally defining the Convoy Effect and listing the disadvantages of FCFS, particularly its unsuitability for time-sharing systems where quick response times are crucial. The instructor uses visual aids like traffic convoy images to make the concept relatable.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the advantages of the FCFS algorithm. The slide titled "Advantage" is visible, listing two key points: "Easy to understand, and can easily be implemented using Queue data structure" and "Can be used for Background processes where execution is not urgent." He verbally explains that because it is simple, it is often the first algorithm taught. He emphasizes that it is good for non-urgent tasks. The "KG" logo is visible in the top right corner.

  2. 2:00 – 5:00 02:00-05:00

    The instructor presents the first numerical example. A table is shown with Process P0 (Arrival Time=0, Burst Time=100) and Process P1 (Arrival Time=1, Burst Time=2). He calculates the Completion Time (CT) for P0 as 100, leading to a Turnaround Time (TAT) of 100 and Waiting Time (WT) of 0. For P1, CT is 102, TAT is 101, and WT is 99. He calculates the Average Waiting Time as (0 + 99) / 2 = 49.5. A Gantt chart is drawn showing P0 running from time 0 to 100, followed by P1 from 100 to 102. He highlights the high waiting time for the short process P1. The formulas TAT=CT-AT and WT=TAT-BT are visible in the table headers.

  3. 5:00 – 10:00 05:00-10:00

    The second numerical example is introduced with swapped arrival times: P0 (AT=1, BT=100) and P1 (AT=0, BT=2). Since P1 arrives first, it executes first. P1 finishes at CT=2, giving TAT=2 and WT=0. P0 finishes at CT=102, giving TAT=101 and WT=1. The new Average Waiting Time is (0 + 1) / 2 = 0.5. The instructor then transitions to a slide titled "Convoy Effect," explaining that smaller processes waiting for larger ones causes high average waiting time. Images of traffic convoys are used as an analogy. A "Disadvantage" slide follows, stating FCFS is troublesome for time-sharing systems. He explains that in time-sharing, users expect quick CPU access, which FCFS fails to provide efficiently. The slide text mentions "FCFS suffers from convoy which means smaller process have to wait larger process".

  4. 10:00 – 10:26 10:00-10:26

    The instructor concludes the lesson by summarizing the comparison. He points out the stark difference between the average waiting times of 49.5 and 0.5 in the two examples. This emphasizes that FCFS performance is highly dependent on the order of arrival and can lead to poor efficiency if long processes arrive early. He reiterates that to achieve less average waiting time, smaller processes should be executed before longer ones. He gestures towards the board to emphasize the point.

The lecture effectively uses a comparative approach to teach FCFS. By presenting two scenarios with identical processes but different arrival orders, the instructor clearly demonstrates the algorithm's sensitivity to input order and its primary flaw: the Convoy Effect. This visual and numerical progression helps students understand why FCFS is often considered inefficient for interactive systems. The use of real-world analogies like traffic convoys further solidifies the concept for the audience. The detailed calculation of average waiting times in both scenarios provides concrete evidence of the algorithm's limitations.

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