Union

Duration: 3 min

This video lesson is available to enrolled students.

Return to /learn/RSSB-INFORMATICS-ASSISTANT/programming-c-oop/structures/structures-declaration-initialization-union-comparison/asset-union after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. Numerical Ability & Problem Solving: Speed Mathematics and Basic Mathematics, Arithmetic, Number System, HCF LCM, Divisibility Rules, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Simple Interest and Compound Interest, Mixture and Alligation, Time and Work, Pipe and Cistern, Speed Time and Distance, Age Problems, Partnership, Data Interpretation, Mental Ability, Sequence and Series (Series), Powers and Exponents (Surds and Indices), Algebra, Statistics, Logarithm, Mensuration and Geometry, Permutation and Combination, Probability, Sequences and Series, Powers, Surds and Logarithms, Subject-Verb Agreement, Sentence Completion, Geometry, Sentence Structure and Correction, Data Sufficiency, Trigonometry, Measurement and Quantity Take-Off, Signal Space and Optimum Detection, Probability, Statistics, Algebra, Time and Work, Speed, Time and Distance, Data Interpretation, Combinatorics
  2. Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Seating Arrangements, Blood Relations, Directions (Direction Test), Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Logical Sequence Of Words, Venn Diagram, Data Arrangement, Inequality, Analogy, Ranking, Order and Sequence, Selection Decision Table (Decision Making), 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, Syllogisms and Venn Diagrams, Critical Reasoning, Order, Ranking and Sequence, Reading Comprehension, Profit, Loss and Discount, Constraint Puzzles, Traverse Surveying, Ratio and Proportion, Mensuration, Permutations and Combinations, Clocks and Calendars, Assembling and Grouping of Shapes, Transformation of Shapes, Three-Dimensional Patterns and Visualization, Cubes and Dice, Vocabulary, Blood Relations
  3. General Knowledge & Current Affairs (India + Rajasthan): History, Geography, Polity, Indian Economy, Static General Knowledge, State Wise GK, GK- Current Affairs, Environment, Physics
  4. Computer Fundamentals & Operating Systems: Basics of COA, Floating Point Rep, Digital Systems & Boolean Basics, Number Representation, Number System, Introduction to OS, File Management, Windows OS, Unix OS, Linux OS, Register Transfer and Microoperations, Virtual Memory
  5. Computer Networks: Introduction to CN, Data Communication, DLL: Error Control, DLL: Access Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Application Layer, Hardware Basics, Network Security
  6. Cyber Security: Cyber Threats and Malware Attacks, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Electronic Data Interchange and E-Commerce, Physical Security and Cryptography Basics, Intrusion Detection Systems (IDS), Cyber Safety and Security, Ethical Hacking
  7. Programming (C & OOP): C Fundamentals, Control Flow, Arrays & Pointers, Functions, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++, Operators & Expressions, Sorting Algorithms, Java Fundamentals, Java
  8. MS Office & Data Processing: MS Office Applications, Basics of DBMS
  9. Internet & Web Technology: Society, Law & Ethics, Terms & Abbreviations, Keyboard Shortcuts, Emerging Tech Trends, Artificial Intelligence, Emerging Technologies, Internet Fundamentals, Website, Browser & Services, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture introduces the Union data structure in C programming as a user-defined datatype that groups variables of different types while sharing the same memory location. The instructor explains that unlike structures, only one member can hold a valid value at any given time because all members occupy the same memory space. The total size of a union is determined by its largest member, illustrated with an example where the character array str[20] dictates a total size of 20 bytes. The lesson demonstrates this behavior through code examples showing how assigning an integer value to one member and then a float to another overwrites the previous data due to shared memory allocation.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor defines a Union in C as a user-defined datatype that groups variables of different data types but shares the same memory location. On-screen text explicitly states 'Groups variables of different datatypes, but shares the same memory location' and 'Only one member can hold a value at a time.' The code snippet `union Data {int i; float f; char str[20];};` is displayed, followed by the declaration `union Data d1; //Total size = 20 bytes.` The instructor annotates member sizes (4B for int, 8B for float) and underlines key phrases to emphasize the shared memory concept. The example `d1.i = 10;` is shown to initialize the union.

  2. 2:00 – 3:14 02:00-03:14

    The lesson continues by demonstrating the overwrite behavior inherent to unions. The instructor shows how assigning a float value, such as `d1.f = 22.5;`, overwrites the previously stored integer value in the same memory space. Visual annotations highlight that the total size remains 20 bytes, determined by the largest member `char str[20]`. The instructor draws arrows to show overlapping memory usage for int, float, and char members. The final code snippet `printf("%d", d1.i);` is presented to illustrate how reading the integer member after a float assignment yields undefined or garbage values due to the shared memory location.

The video provides a foundational understanding of C unions by contrasting them with structures through memory allocation principles. The core concept is that union members share the same physical address, meaning writing to one member invalidates previous values in other members. The size calculation is strictly based on the largest member, ensuring sufficient space for any single type within the union. This behavior is critical for memory-efficient programming where only one data type needs to be stored at a time. The examples clearly show the practical implications of this design, such as data overwriting when switching between int and float assignments within the same union variable.

Loading lesson…