Union

Duration: 3 min

This video lesson is available to enrolled students.

Return to /learn/UP-LT-GRADE-ASSISTANT-TEACHER-2025/cs-04-problem-solving-through-c-programming/structures/structures-declaration-initialization-union-comparison/asset-union after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. CS | 01 | Digital Logic and Circuits and Discrete Mathematical Structures: Digital Systems & Boolean Basics, Number System, Number Representation, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Permutation and Combination
  3. CS | 02 | Computer Organization and Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Multiprocessors
  4. CS | 03 | Data Structures and Algorithm: 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, Complexity Theory, Advanced Algorithms
  5. CS | 04 | Problem Solving through C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  6. CS | 05 | Object Oriented Techniques: Object Oriented Technology, Java
  7. CS | 06 | 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, Unix OS
  8. CS | 07 | Database Management Systems: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, Database Security & Authorization, Query Processing & Optimization, File Organization & Indexing
  9. CS | 08 | 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
  10. CS | 09 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  11. CS | 10 | Internet Technology, Web Design and Web Technology: Internet Fundamentals, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, JavaScript-Basics, HTML Basics
  12. CS | 11 | System Analysis And Design: Fundamentals of Systems and Information Systems, SDLC and Development Approaches, Software Documentation and Software Requirements Specification (SRS), SDD and Quality Assurance, Security, Risk Management & Maintenance
  13. CS | 12 | Information Security and Cyber Laws: 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
  14. CS | 13 | Computer Graphics: Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing
  15. GS Paper | 01 | Indian and World Geography: Geography
  16. GS Paper | 02 | History: History
  17. GS Paper | 03 | Indian Economy & Social Development: Indian Economy
  18. GS Paper | 04 | General Science: Biology, Chemistry, Physics
  19. GS Paper | 05 | Elementary Maths: Number System, Divisibility Rules, HCF LCM, Percentage, Profit and Loss, Simple Interest and Compound Interest, Ratio and Proportion (Ratios), Average, Time and Work, Speed Time and Distance, Algebra, Mensuration and Geometry, Data Interpretation, Arithmetic, Statistics, Probability, Sequence and Series (Series), Mixture and Alligation, Calculus, Trigonometry, Vectors
  20. GS Paper | 06 | Indian Polity and Governance: Polity
  21. GS Paper | 07 | Current Events: GK- Current Affairs
  22. UPLT Live Classes Notes: UPLT Live Classes
  23. UPLT Full Mock Tests Tier 1:
  24. UPLT Full Mock Tests Tier 2:
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…