C Union

Union Declaration

Union is a composite data type that allows you to store different types of data in the same memory location. It is similar to a structure ('struct') in that it can hold multiple variables of different data types, but unlike a 'struct', a union can only store the value of one of its members at a time. This means that the size of a union is determined by the size of its largest member.

Here's how you declare a union in C:

union union_name {
    data_type member1;
    data_type member2;
    // Additional members
};

Breakdown of mentioned union syntax:

⤑ 'union_name': The name of the union.

⤑ 'data_type': The data type of each member.

You can have multiple members in a union, Here's an example of how you might use a union:

#include ＜stdio.h>
#include ＜string.h>

// Define a union named Data
union Data {
    int i;
    float f;
    char str[20];
};

int main() {
    union Data data;

    // Store an integer in the union
    data.i = 10;
    printf("Integer value: %d\n", data.i);

    // Store a floating-point number in the same union
    data.f = 3.14;
    printf("Float value: %f\n", data.f);

    // Store a string in the union
    strcpy(data.str, "Hello, Friend!");
    printf("String value: %s\n", data.str);

    return 0;
}

In this program, we define a union called 'Data' with three members: an integer ('i'), a floating-point number ('f'), and a character array ('str'). We then demonstrate how to store and access different types of data in the same union. Please note that when you assign a value to one member of the union, it may affect the value of other members because they all share the same memory location. This is a key characteristic of unions.

Integer value: 10
Float value: 3.140000
String value: Hello, Friend!

As you can see, each time we assign a value to a member of the union, it overwrites the previous value in the union's memory. This is why the values of the integer, float, and string are displayed correctly in the output.