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Introduction
What is C Identifiers Characters in C Datatypes & Variables Structure of C Program How to install turbo C in windows XP? How to install turbo C in windows 7/8?
Introduction [cont'd]
How to Compile and Run? Header files C Tokens Escape sequence Keywords Storage class specifier Constants
Introduction [cont'd]
Volatile
Operators
Operators Arithmetic Operators Relational operators Logical operators Increment & Decrement Operators Assignment Operators Bitwise operators
Operators [cont'd]
Conditional Operator Sizeof Operator
Input Output Functions
printf Scanf Getch putch getche Putchar getchar
Input Output Functions [cont'd]
gets puts
Decision Statements
If If-Else Else-If Nested If-Else Switch Goto
Looping Statements
For While Do-While Break Continue
Arrays
What is Array? One Dimensional Two Dimensional Multi Dimensional
Strings
What is String? Strlen Strcpy Strcmp Strlwr Strupr Strchr
Strings [cont'd]
Strstr Strcat Strrev
User-defined Functions
What is Functions? Function prototype Defining a Function Simple Arguments Return Value Arguments with Return value
User-defined Functions [cont'd]
Call by value Call by reference Recursion Nesting Functions Arrays as Arguments
Structures and Unions
Define Structure Copying Structures Comparing two Structures Arrays of Structures Nested Structures Structure with Functions Define Union
Structures and Unions [cont'd]
Different between Struct and Union
Pointers
Define Pointers & Operator Operators in pointers Pointers Array Pointers as Function Arguments Functions Returning Pointers Pointers and Structures
Memory
Dynamic Memory Allocation Malloc Calloc Realloc Free
Files
What is Files? Write Files Read Files Append Files Error handling
# Preprocessor
What is preprocessor in C? #include #define #if and #else #elif #ifdef #ifndef
# Preprocessor [cont'd]
#undef
Define Union in Structures and Unions of Programming in C
2244 Views
Define Union 
Union is also same as structure. But union is a shared memory, It is possible to assign and retrieve only one member value at a time. Next member value will collapse previous member data. Memory size shall be maximum size of a member.

Example
Union student{
int rno;
char student_name[20];
};

For above union example allocates 20 bytes.
Syntax 
union union_name
{
variables declaration;
};
Program
	#include
	//Allocates maximum memory needed by union members - 20 bytes
	//Set and Get the values from union immediatly
	union product {
	   int product_no;
	   char product_name[20];
	   float amount;
	};
	void main(){
	   union product pro;
	   pro.product_no = 123;
	   printf("%d\n",pro.product_no);
	   //When setting value for next member this collapse all other values of other members
	   //Union is a shared memory
	   strcpy(pro.product_name,"Dove");
	   printf("%d : %s",pro.product_no,pro.product_name);
	   pro.amount = 29.00f;
	   printf("%d : %s : %5.2f",pro.product_no,pro.product_name,pro.amount);
	}
Output 
123
28484 : Dove
0 : : 29.00
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