Disk Basics

Duration: 32 min

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Inside: a video lesson and guided study material.

Module outline

  1. Course Overview: About the Course
  2. Paper - 1 | Unit - 1 | Teaching Aptitude: शिक्षण की अवधारणा एवं उद्देश्य / Concept and Objectives of Teaching, शिक्षण के स्तर / Levels of Teaching, शिक्षार्थी की विशेषताएँ / Learner's Characteristics, अधिगम: प्रकृति एवं सिद्धांत / Learning: Nature and Theories, संज्ञान, स्मृति एवं अधिसंज्ञान / Cognition, Memory and Metacognition, शिक्षण को प्रभावित करने वाले कारक / Factors Affecting Teaching, प्रभावी शिक्षण एवं शिक्षक / Effective Teaching and the Teacher, अनुदेशनात्मक उद्देश्य एवं पाठ नियोजन / Instructional Objectives and Lesson Planning, शिक्षण विधियाँ / Methods of Teaching, ऑफ़लाइन एवं ऑनलाइन शिक्षण विधियाँ / Offline and Online Teaching Methods, शिक्षण सहायक प्रणाली / Teaching Support System, मूल्यांकन प्रणाली / Evaluation Systems, Sāṃkhya, व्यक्तिगत व्यवहार / Individual Behaviour, मानव संसाधन प्रबंधन / Human Resource Management, बाल्यावस्था में विकास के क्षेत्र / Domains of Child Development, संवेग का जैविक आधार / Biological Basis of Emotion, उपनिषद और भगवद्गीता / Upanishads and Bhagavad Gita, केन्द्रीय और परिधीय तंत्रिका तंत्र / Central and Peripheral Nervous Systems
  3. Paper - 1 | Unit - 2 | Research Aptitude: अनुसंधान: अर्थ, लक्षण व वैज्ञानिक विधि / Research: Meaning, Features and Scientific Method, अनुसंधान के प्रतिमान एवं उपागम / Research Paradigms and Approaches, अनुसंधान के प्रकार / Types of Research, चर एवं मापन / Variables and Measurement, अनुसंधान की विधियाँ / Methods of Research, अनुसंधान के चरण / Steps of Research, प्रतिचयन / Sampling, आँकड़ा संग्रह के उपकरण एवं विधियाँ / Tools and Methods of Data Collection, आँकड़ा विश्लेषण एवं शोध सांख्यिकी / Data Analysis and Statistics in Research, शोध-प्रबंध एवं लेख लेखन / Thesis and Article Writing, अनुसंधान में ICT का अनुप्रयोग / Application of ICT in Research, शोध नैतिकता / Research Ethics
  4. Paper - 1 | Unit - 3 | Comprehension: प्रत्यक्ष बोध / Literal Comprehension, गद्यांश में शब्दावली और भाषा / Vocabulary and Language in Context, निष्कर्षात्मक बोध / Inferential Comprehension, आलोचनात्मक बोध / Critical Comprehension, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Restoration and Eighteenth-Century Drama, Modern British Fiction, William Shakespeare, Mid-Twentieth-Century and Contemporary British Fiction, American Drama
  5. Paper - 1 | Unit - 4 | Communication: संचार: अर्थ, प्रकृति एवं प्रक्रिया / Communication: Meaning, Nature and Process, संचार के प्रकार एवं स्तर / Types and Levels of Communication, मौखिक एवं अमौखिक संचार / Verbal and Non-verbal Communication, संकेत विज्ञान एवं अर्थ / Semiotics and Meaning, संचार के मॉडल एवं सिद्धांत / Models and Theories of Communication, प्रभावी संचार / Effective Communication, संचार की बाधाएँ / Barriers to Communication, कक्षा संचार / Classroom Communication, जनसंचार माध्यम: प्रकार एवं विकास / Mass Media: Types and Evolution, जनसंचार एवं समाज / Mass Media and Society, डिजिटल एवं नव माध्यम / Digital and New Media, Static General Knowledge, Morphology and Syntax, जन स्वास्थ्य पोषण / Public Health Nutrition, Newtonian Motion and Stability, GK- Current Affairs, Indian Economy, Art and Architecture, India after Independence
  6. Paper - 1 | Unit - 5 | Mathematical Reasoning and Aptitude: संख्या पद्धति एवं सरलीकरण / Number System and Simplification, बीजगणित एवं आयु / Algebra and Ages, प्रतिशतता / Percentage, अनुपात, समानुपात, साझेदारी एवं मिश्रण / Ratio, Proportion, Partnership and Mixtures, औसत / Averages, लाभ, हानि एवं बट्टा / Profit, Loss and Discount, साधारण एवं चक्रवृद्धि ब्याज / Simple and Compound Interest, समय एवं कार्य / Time and Work, चाल, समय एवं दूरी / Speed, Time and Distance, क्षेत्रमिति एवं ज्यामिति / Mensuration and Geometry, श्रेणी / Series, कूटलेखन-कूटवाचन / Coding-Decoding, संबंध, दिशा एवं क्रम / Relationships, Directions and Ranking, व्यवस्था, पहेलियाँ, घड़ी एवं कैलेंडर / Arrangements, Puzzles, Clock and Calendar, Mathematical Foundations, Polity, जीवनी, Deconstruction, Gender and Queer Theory, Modern British and Irish Poetry, Central Force and Scattering, Chemical thermodynamics, Microscopic techniques, संविधान का दर्शन / Philosophy of the Constitution, Waves, Optics and Charged-Particle Motion, Membrane structure and function, Analysis
  7. Paper - 1 | Unit - 6 | Logical Reasoning: युक्ति की संरचना / Structure of Arguments, पद, परिभाषा एवं भाषा के उपयोग / Terms, Definitions and Uses of Language, निरुपाधिक प्रतिज्ञप्तियाँ / Categorical Propositions, निरुपाधिक न्यायवाक्य / Categorical Syllogism, वेन आरेख / Venn Diagrams, निगमन, आगमन एवं सादृश्यता / Deduction, Induction and Analogy, तर्कदोष / Fallacies, भारतीय तर्कशास्त्र: प्रमाण / Indian Logic: Pramanas, अनुमान एवं व्याप्ति / Anumana and Vyapti, हेत्वाभास / Hetvabhasa, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Aristotle, पाश्चात्य दर्शन की विचारधाराएँ / Western Schools of Philosophy, Kant, Sadhana Paada, Vaiśeṣika
  8. Paper - 1 | Unit - 7 | Data Interpretation: आँकड़े एवं आलेखीय निरूपण / Data and Graphical Representation, आँकड़ा निर्वचन: तालिका / Data Interpretation: Tables
  9. Paper - 1 | Unit - 8 | Information and Communication Technology: कंप्यूटर की मूल बातें और हार्डवेयर / Computer Fundamentals and Hardware, मेमोरी, भंडारण और डेटा निरूपण / Memory, Storage and Data Representation, कंप्यूटर सॉफ्टवेयर / Computer Software, ऑफिस अनुप्रयोग / Office Applications, मल्टीमीडिया और फ़ाइल प्रारूप / Multimedia and File Formats, कंप्यूटर नेटवर्क / Computer Networks, इंटरनेट और वर्ल्ड वाइड वेब / Internet and World Wide Web, ई-मेल और ऑनलाइन संचार / Email and Online Communication, साइबर सुरक्षा / Cyber Security, डिजिटल नैतिकता, बौद्धिक संपदा और समाज / Digital Ethics, IPR and Society, क्लाउड और वितरित कंप्यूटिंग / Cloud and Distributed Computing, उभरती प्रौद्योगिकियाँ / Emerging Technologies, शिक्षा और शासन में ICT / ICT in Education and Governance, Cyber Threats and Malware Attacks, Role of Internet and Web Services, Electronic Data Interchange and E-Commerce, Internet Fundamentals, Web Design & Development, Web Publishing & Hosting, Emerging Technologies, Terms & Abbreviations, Society, Law & Ethics, Keyboard Shortcuts, Website, Browser & Services, भौगोलिक संकेतों का संरक्षण / Protection of Geographical Indications
  10. Paper - 1 | Unit - 9 | People Development and Environment: पारितंत्र और जैव विविधता / Ecosystems and Biodiversity, मानव और पर्यावरण की अंतःक्रिया / Human and Environment Interaction, विकास और पर्यावरण / Development and Environment, प्राकृतिक संसाधन: वन, जल और मृदा / Natural Resources – Forests, Water and Soil, ऊर्जा संसाधन / Energy Resources, वायु प्रदूषण / Air Pollution, जल प्रदूषण और उपचार / Water Pollution and Treatment, ध्वनि प्रदूषण / Noise Pollution, अपशिष्ट प्रबंधन / Waste Management, पर्यावरणीय स्वास्थ्य और विषविज्ञान / Environmental Health and Toxicology, जलवायु परिवर्तन और वैश्विक पर्यावरणीय समस्याएँ / Climate Change and Global Environmental Issues, प्राकृतिक प्रकोप और आपदा प्रबंधन / Natural Hazards and Disaster Management, भारतीय पर्यावरण कानून और नीतियाँ / Indian Environmental Laws and Policies, अंतर्राष्ट्रीय पर्यावरण समझौते / International Environmental Agreements, Environment, Geography, कारखाना और उद्योग व्यवस्थाएँ / Factory and Industry Systems, Earth Materials, Surface Features and Processes, संक्रामक रोग और प्रतिरक्षण / Communicable Diseases and Immunization
  11. Paper - 1 | Unit - 10 | Higher Education System: प्राचीन भारत में शिक्षा / Education in Ancient India, प्राचीन भारत के उच्च शिक्षा केंद्र / Ancient Centres of Higher Learning, औपनिवेशिक काल की शिक्षा नीतियाँ और आयोग / Colonial Education Policies and Commissions, औपनिवेशिक कॉलेज, विश्वविद्यालय व सुधारक / Colonial Colleges, Universities and Reformers, स्वतंत्र भारत में शिक्षा आयोग और नीतियाँ / Education Commissions and Policies after Independence, राष्ट्रीय शिक्षा नीति 2020 / National Education Policy 2020, उच्च शिक्षा संस्थानों के प्रकार / Types of Higher Education Institutions, अधिगम कार्यक्रम और अकादमिक क्रेडिट / Learning Programmes and Academic Credits, व्यावसायिक, तकनीकी और कौशल आधारित शिक्षा / Professional, Technical and Skill-Based Education, मूल्य शिक्षा और पर्यावरण शिक्षा / Value Education and Environmental Education, शासन, प्रशासन और वित्तपोषण / Governance, Administration and Financing, उच्च शिक्षा का नियमन, प्रत्यायन और रैंकिंग / Regulation, Accreditation and Ranking
  12. Paper 2 | Unit 1 | Discrete Structures and Optimization: Propositional and Predicate Logic, Set Theory, Relations, Functions, क्रमचय, संचय एवं प्रायिकता / Permutation, Combination and Probability, Graph Theory, Group Theory, Digital Systems & Boolean Basics, Boolean Expression, Boolean Minimization, Optimization, Markov Chains
  13. Paper 2 | Unit 2 | Computer System Architecture: Logic Gates & Hardware, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep, Basics of COA, Register Transfer and Microoperations, Programming the Basic Computer, Instr Formats & Modes, Control Unit Design, Pipelining, Input Output Organisation, Cache Memory Organization, Multiprocessors
  14. Paper 2 | Unit 3 | Programming Languages and Computer Graphics: Language Design, C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, HTML Basics, XML, JavaScript-Basics, Java, Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing, OOPS with C++, Java Fundamentals, Array, String, IO & References, OOPS with Java
  15. Paper 2 | Unit 4 | Database Management Systems: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, ORDBMS, Database Security & Authorization, Query Processing & Optimization, Enhanced Data Models, Data Warehousing & Mining, Big Data Systems, NoSQL
  16. Paper 2 | Unit 5 | System Software and Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Linux OS, Security, Distributed Systems, Virtual Machines
  17. Paper 2 | Unit 6 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  18. Paper 2 | Unit 7 | Data Structures and Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  19. Paper 2 | Unit 8 | Theory of Computation and Compilers: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines, Complexity Theory, 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
  20. Paper 2 | Unit 9 | Data Communication and 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, Hardware basics, Network Security, Mobile Technology, Cloud Computing and IoT, Cloud Computing
  21. Paper 2 | Unit 10 | Artificial Intelligence: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Fuzzy Sets, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms
  22. Live Classes: NTA UGC NET 2025 Live Class
  23. Paper 1 | Full Mock Tests:
  24. Paper 2 | Full Mock Tests:
  25. Paper 1 | Previous Year Papers:
  26. Paper 2 | Previous Year Papers:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture introduces disk storage fundamentals, progressing from general secondary and optical storage to the internal mechanics of magnetic hard disk drives (HDDs) and finally to quantitative access-time calculations. The instructor begins by defining secondary storage as non-volatile, permanent, and high-capacity, contrasting it with RAM. Examples include HDDs, SSDs, magnetic tape, and optical media such as CDs, DVDs, and Blu-ray discs. The lesson then focuses on magnetic disks, explaining that data is stored magnetically on rotating platters and organized into tracks, sectors, and cylinders. Using a labeled HDD diagram and hand-drawn concentric-circle diagrams, the instructor maps physical components—platters, spindles, read/write heads, and actuator arms—to logical structures. A worked example with two platters shows that the number of surfaces equals 2 × 2 = 4, distinguishing upper and lower surfaces. The lecture then introduces logical blocks and Logical Block Addresses (LBA), stating that a logical block is the smallest unit of data transfer and that logical blocks are mapped to physical sectors in a defined order: track, cylinder, then next cylinder. Finally, the instructor defines disk access time as seek time plus rotational latency plus data transfer time plus controller overhead. Using a 6000 RPM disk, the rotation time is calculated as 60 / 6000 = 0.01 seconds, or 10 ms per rotation, and average rotational latency is half of that. A sample problem with seek time 8 ms, transfer time 2 ms, and overhead 1 ms is set up to compute total data access time.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The lecture opens with a 'Storage Basics' slide defining secondary storage as used to store data permanently, non-volatile so data remains when power is off, and providing large storage capacity. The instructor underlines 'permanently' and writes 'Unlike RAM' in pink ink to contrast secondary storage with primary memory. Examples shown include Hard Disk (HDD), Solid State Drive (SSD), and Magnetic Tape, alongside optical storage devices such as CD, DVD, and Blu-ray Disc. The instructor points to the optical storage section and notes that it is a direct-access device, using arrows to connect text descriptions to the corresponding device images.

  2. 2:00 – 5:00 02:00-05:00

    The instructor continues annotating the storage basics slide, highlighting 'non-volatile' and adding handwritten notes about SSD capacities such as 1TB, 2TB, and 3TB. Magnetic tape is circled among the secondary storage examples. The lesson then transitions to a new slide titled 'Magnetic Disk,' which states that magnetic disks provide a large part of secondary storage, that the Hard Disk Drive (HDD) is the most common magnetic disk, and that data is stored magnetically on rotating platters. A labeled HDD diagram appears showing the Platter, Spindle, Read/Write Head, and Actuator Arm, with a magnified inset of concentric rings labeled Track and Sector and a stacked-platter graphic tagged Cylinder.

  3. 5:00 – 10:00 05:00-10:00

    The instructor points to the exploded HDD diagram and underlines key phrases in pink, including 'magnetic disk' on the second bullet. The magnified inset shows concentric rings labeled Track and Sector beside a platter stack labeled Cylinder, with pink handwritten notes. To clarify disk organization, the instructor draws a pink concentric-circle diagram on the board and adds an arrow labeled 'Track.' This visual bridge connects the physical platter layout to the logical arrangement of data, emphasizing that tracks are concentric rings on a disk surface and sectors divide each track into smaller units.

  4. 10:00 – 15:00 10:00-15:00

    At the interactive whiteboard, the instructor draws a pink target-like diagram labeled 'Tracks' and 'Sector.' He writes 'No of Platters = 2' and calculates 'No of Surfaces = 2 x 2 = 4,' then sketches two pairs of concentric circles bracketed as 'Platter 0' and 'Platter 1,' labeling each pair with Upper Surface and Lower Surface. The slide states that a disk is organized into Tracks, Sectors, and Cylinders, and notes that an HDD contains moving parts such as platters and read/write heads. The cylinder concept is reinforced visually as a stack of corresponding tracks across multiple platters.

  5. 15:00 – 20:00 15:00-20:00

    The lecture moves to a slide titled 'Logical Blocks and LBA,' which states that a logical block is the smallest unit of data transfer. A 'Magnetic Disk Structure' diagram labels Track, Read/Write Head, and Actuator Arm. A Block-to-LBA table maps Block 0 through Block 5 to LBA 0 through LBA 5, and a 'Mapping Order' column shows Track, Cylinder, then Next Cylinder. A right-hand 'Key Points' panel lists numbered points including that logical blocks are mapped to the physical sectors of the disk. The instructor then turns to the whiteboard and draws concentric circles in pink marker, repeating the pattern as two sets labeled 'Upper Side' and 'Lower Side,' joined by a bracket marked 'Platters.'

  6. 20:00 – 25:00 20:00-25:00

    The instructor explains the mapping of logical blocks to physical sectors on the whiteboard, using the 'Logical Blocks and LBA' slide with its magnetic disk structure diagram and mapping order. He then introduces 'Disk Access Time,' defining seek time and rotational latency as the main components of access delay. On the whiteboard he writes formulas: '1 Rotation Time = 60 / RPM seconds' and 'Average Rotational Latency = 1/2 x Rotation Time.' A hand-drawn disk rotation diagram illustrates how the read/write head must wait for the desired sector to rotate into position, making average latency half of one full rotation.

  7. 25:00 – 30:00 25:00-30:00

    The instructor applies the access-time formulas to a concrete example. A slide shows circled terms 'Seek Time' and 'Rotational Latency,' a hand-drawn concentric disk diagram, and the note 'Rotational Speed = 6000 RPM.' A question slide states that a disk has a rotational speed of 6000 RPM, with seek time 8 ms, transfer time 2 ms, and controller overhead 1 ms. In pink marker the instructor computes '1 Sec = 6000/60 = 100' rotations per second and a round time of '10ms,' establishing the rotation period needed to find average rotational latency.

  8. 30:00 – 32:26 30:00-32:26

    The final segment consolidates the access-time calculation. The slide presents the formula 'Data Access Time = Seek Time + Rotational Latency + Data Transfer + Overhead.' Using the 6000 RPM disk, one rotation takes 10 ms, so average rotational latency is 5 ms. The instructor combines the given values—seek time 8 ms, average rotational latency 5 ms, transfer time 2 ms, and overhead 1 ms—to compute total data access time. This worked example ties together the physical disk structure, logical block mapping, and timing formulas introduced earlier in the lecture.

The lecture builds a coherent model of disk storage from abstract to quantitative. It starts by situating secondary storage within the memory hierarchy: non-volatile, permanent, and high-capacity, with HDDs, SSDs, tape, and optical media as examples. The focus then narrows to magnetic disks, where the physical components (platters, spindle, read/write head, actuator arm) are mapped to logical structures (tracks, sectors, cylinders). The two-platter example clarifies that each platter has an upper and lower surface, giving four surfaces total. Logical blocks and LBA provide the software-visible abstraction: a logical block is the smallest transfer unit, mapped to physical sectors in track-cylinder-next cylinder order. The quantitative portion defines disk access time as seek time plus rotational latency plus transfer time plus overhead, with rotation time equal to 60/RPM seconds and average rotational latency half of that. The 6000 RPM example yields a 10 ms rotation and 5 ms average latency, which is then added to the given seek, transfer, and overhead values. For exam revision, students should remember the definitions of non-volatile secondary storage, the track-sector-cylinder hierarchy, the LBA mapping order, and the access-time formula with its RPM-based latency calculation.

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