Address Operation - Substraction

Duration: 2 min

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Module outline

  1. English Comprehension: Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Reading Comprehension, Vocabulary, Idioms and Phrases, Narrative Sequencing, Critical Reasoning
  2. Reasoning and Aptitude: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Analogy, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Blood Relations, Directions (Direction Test), Ranking, Order and Sequence, Logical Sequence Of Words, Seating Arrangements, Puzzle Solving (Puzzles), Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Data Sufficiency, Selection Decision Table (Decision Making), Calendar, Clock, Cubes & Dices, Data Arrangement, Venn Diagram, Analytical Reasoning (Counting Figures Reasoning), Number System, HCF LCM, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Simple Interest and Compound Interest, Speed Time and Distance, Mensuration and Geometry, Arithmetic, Mixture and Alligation, Age Problems, Data Interpretation, Alphabet and Word Tests, Numerical Reasoning, Number System, Averages, Mixtures and Alligation, Percentages, Series Completion, Analogy and Classification, Patterns in Two-Dimensional Figures, Coding and Decoding, Mathematical Operations, Direction Sense, Logical Deduction and Induction, Simplification and Approximation, Assembling and Grouping of Shapes, Transformation of Shapes, Three-Dimensional Patterns and Visualization, Cubes and Dice, Algebra, Traverse Surveying, Clocks and Calendars, Order, Ranking and Sequence, Constraint Puzzles, Syllogisms and Venn Diagrams, Ratio and Proportion, Mensuration, Permutations and Combinations, Project Monitoring, Resources and Safety, Profit, Loss and Discount, Sequences and Series, Powers, Surds and Logarithms, Subject-Verb Agreement, Sentence Completion, Geometry, Probability, Trigonometry, Measurement and Quantity Take-Off, Statistics, Data Sufficiency, Blood Relations, Speed, Time and Distance, Time and Work, Data Interpretation, Sequence and Series (Series), Algebra, Permutation and Combination, Combinatorics
  3. General Awareness: Physics, Chemistry, Biology, Geography, History, Polity, Indian Economy
  4. Computer Fundamentals: Basics of COA, Number System, Number Representation, Semiconductor Memories and Programmable Logic, Timing, Hazards and Testing, Processor Organization and Instructions, Number Systems and Codes, Combinational Logic Design, Combinational Logic Circuits, Number Systems and Codes
  5. Operating System: Introduction to OS, Unix OS, Linux OS
  6. C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  7. OOPS with C++ & Java: OOPS with C++, Java
  8. Database Management System: Basics of DBMS, SQL
  9. MS Office: MS Office Applications
  10. Internet & Web Technologies: Website, Browser & Services, Internet Fundamentals, Web Design & Development, Protocols & Services
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.

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