Address Operation - Substraction

Duration: 2 min

This video lesson is available to enrolled students.

Return to /learn/RSSB-BASIC-COMPUTER-INSTRUCTOR/paper-2-programming-fundamentals/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 the Course: About the Course
  2. Paper-1 & 2 | Basic Numeracy: Ratio and Proportion (Ratios), Divisibility Rules, Mixture and Alligation, Permutation and Combination, Logarithm, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Percentage, Average, Mensuration and Geometry, Age Problems, Arithmetic, Statistics, Probability, Profit and Loss, Simple Interest and Compound Interest, Partnership, Speed Mathematics and Basic Mathematics, Algebra, Powers and Exponents (Surds and Indices), Time and Work, Pipe and Cistern, RSSB Specific Videos - Basic Numeracy
  3. Paper-1 & 2 | Data Interpretation: Data Interpretation
  4. Paper-1 & 2 | General Mental Ability: Mental Ability, RSSB Specific Videos - Mental Ability
  5. Paper-1 & 2 | Logical Reasoning and Analytical Ability: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Syllogisms, Seating Arrangements, Blood Relations, Directions (Direction Test), Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Venn Diagram, Analogy, Ranking, Order and Sequence, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Data Arrangement, Logical Sequence Of Words, Crypt Arithmetic
  6. Paper-1 & 2 | Decision Making and Problem Solving: Selection Decision Table (Decision Making)
  7. Paper-1 | General Science: Physics, Biology, Chemistry, RSSB Specific Videos
  8. Paper-1 | General Awareness: State Wise GK, GK- Current Affairs
  9. Paper - 2 | Digital Logic Systems: Digital Systems & Boolean Basics, Logic Gates & Hardware, Combinational Circuit, Sequential Circuits
  10. Paper-2 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Calculus, Relational Algebra, SQL, NoSQL
  11. Paper-2 | Data Structures & Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Algorithm Analysis, Sorting Algorithms, Intro to Compilers, Hashing
  12. Paper 2 | Data Communication and Network Security: Introduction to CN, Data Communication, Data Link Layer - Ethernet, DLL: Error Control, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Application Layer, Hardware basics, Network Security, Ethical Hacking
  13. Paper-2 | Operating Systems: Introduction to OS, Process Management, Memory Management, File Management, Deadlock
  14. Paper-2 | Computer Organization and Architecture: 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, Number System, Number Representation
  15. Paper 2 | System Analysis and Design: Fundamentals of Systems and Information Systems, Fundamentals of Software Engineering, SDLC and Development Approaches, Software Documentation and Software Requirements Specification (SRS), SDD and Quality Assurance, Security, Risk Management & Maintenance, Software Testing
  16. Paper-2 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  17. Paper 2 | OOPS , C++ , JAVA: Language Design, OOPS with C++, Java, .Net Programming, Java Fundamentals
  18. Paper 2 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis
  19. Emerging Trends and AI: Emerging Tech Trends, Artificial Intelligence
  20. Paper-2 | Data Processing (Ms-Office): MS Office Applications
  21. Paper-2 | Internet and Web Technologies: HTML Basics, CSS, XML, JavaScript-Basics, Internet Fundamentals, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, Terms & Abbreviations, Cyber Threats and Malware Attacks, Role of Internet and Web Services, Security in Mobile and Wireless Computing
  22. Paper 2 | Pedagogy: Child Development, Theories, Concept of Pedagogy, Inclusive Education, Experiential Pedagogy, Assessment & Evaluation, Psychology, Curriculum Framework & Reforms, National Education Policy (NEP) 2020
  23. Live Classes: RSSB Live Sessions
  24. Paper 1 - Full Mock Tests:
  25. Paper 2 - Full Mock Tests:
  26. BCI Previous Year Papers:
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…