Structure:

In C programming, structures (often referred to as "structs") are user-defined data types that allow you to group together different variables under a single name. A structure can hold various types of data such as integers, floats, arrays, and even other structures, enabling you to create more complex data structures.

This code uses a structure

Here m is the structure variable used to access elements of the structure

 

The same program can be written using a union to get the same result.

 


The difference between structures and unions is:

 

Though unions are similar to structure in so many ways, the difference between them is

crucial to understand. This can be demonstrated by this example:

 

#include <stdio.h>

union job

{

    char name[32];

    float salary;

    int worker_no;

}u;

 

struct job1

{

    char name[32];

    float salary;

    int worker_no;

}s;

 

int main()

{

    printf("size of union = %d",sizeof(u));

    printf("\nsize of structure = %d", sizeof(s));

    return 0;

}


Output:


size of union = 32 size of structure = 40




There is difference in memory allocation between union and structure as suggested in above example. The amount of memory required to store a structure variable is the sum of memory size of all members.

But, the memory required to store a union variable is the memory required for largest element of an union.

 

Also, all members of structure can be accessed at any time. But, only one member of union can be accessed at a time. In case of union other members will contain garbage value.