Address Operation - Substraction

Duration: 2 min

This video lesson is available to enrolled students.

Return to /learn/COAL-INDIA-MANAGEMENT-TRAINEE/programming-data-structures/arrays-pointers/relationship-between-arrays-and-pointers/asset-address-operation-substraction after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. Paper-2 | Programming & Data Structures: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  3. Paper-2 | Databases / DBMS & SQL: 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
  4. Paper-2 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  5. Paper-2 | Computer Networks & Security: 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 Access Technologies, Network Security
  6. Paper-2 | Digital Logic: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep
  7. Paper-2 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management
  8. Paper-2 | 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
  9. Paper-2 | Computer Organization & Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer
  10. Paper-2 | 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. Paper-1 | General Awareness: Polity, Physics, Biology, Chemistry, Static General Knowledge, GK- Current Affairs, History, Geography, Indian Economy, Environment
  12. Paper-1 | Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Data Interpretation, Blood Relations, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Clock, Calendar, Cubes & Dices, Directions (Direction Test), Analogy, Seating Arrangements, Analytical Reasoning (Counting Figures Reasoning)
  13. Paper-1 | Quantitative Aptitude: Ratio and Proportion (Ratios), Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Speed Time and Distance, Average, Age Problems, Percentage, Profit and Loss, Time and Work, Pipe and Cistern, Simple Interest and Compound Interest, Powers and Exponents (Surds and Indices), Mensuration and Geometry, Probability, Statistics, Arithmetic, Algebra
  14. Paper-1 | English: Vocabulary, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Construction, Cloze Test (Cloze Passage)
  15. Coal India Previous Year Paper:
  16. Engineering Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Linear Algebra, Calculus
  17. Coal India Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture segment introduces pointer subtraction in C programming, specifically focusing on subtracting a constant from an address. The instructor explains that when a constant is subtracted from a pointer, the pointer moves backward by multiples of its data type's size. The syntax `ptr = ptr - n;` is presented as the standard method for this operation. A concrete example uses an integer array `int arr[5] = {10, 20, 30, 40, 50};` where a pointer `p` is initialized to the fourth element (`&arr[3]`). By executing `p = p - 1;`, the pointer moves back one integer size to point to `arr[2]`. Visual aids include hand-drawn memory diagrams and on-screen text calculations showing address changes, such as moving from address 1006 to 1004 assuming a 2-byte integer size.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video begins by defining pointer subtraction rules, stating that subtracting a constant moves the pointer backward by `n * sizeof(data_type)`. On-screen text displays the syntax `ptr = ptr - n;` alongside an integer array example. The instructor sketches a hand-drawn memory diagram to visualize the array structure, showing elements 10 through 50. A pointer `p` is initialized to index 3 (`&arr[3]`). The operation `p = p - 1;` is demonstrated, resulting in the pointer moving from index 3 to index 2. The visual evidence confirms that the address changes based on the data type size, with text explicitly noting `p now points to arr[2], i.e., address of 30`.

  2. 2:00 – 2:19 02:00-02:19

    In the final segment, the lesson concludes with a specific numerical calculation of pointer arithmetic. The instructor shows that subtracting 1 from the pointer `p` (initialized at address 1006) results in a new address of 1004. This calculation is derived from the formula `1006 - 1 * 2 = 1004`, explicitly assuming a 2-byte integer size. The on-screen text reiterates the rule that pointers move backward by multiples of their data type's size. The visual diagram reinforces this by showing the pointer shifting from index 3 back to index 2, confirming that `p` now points to the address of value 30.

The lecture effectively demonstrates pointer subtraction by combining syntax rules with visual memory diagrams. The core concept is that `ptr - n` moves the pointer backward by `n * sizeof(type)`. The example of decrementing an integer pointer from index 3 to 2 serves as a practical application, showing how address arithmetic works in memory. The calculation `1006 - 2 = 1004` provides a concrete numerical verification of the theoretical rule. This progression from abstract syntax to specific memory addresses ensures students understand both the code and the underlying hardware behavior.

Loading lesson…