Union in C

Union can be defined as a user-defined data type which is a collection of different variables of different data types in the same memory location. The union can also be defined as many members, but only one member can contain a value at a particular point in time.

Union in C

• Declaration:
  union union_name {
      data_type member1;
      data_type member2;
      // ...
  };
  

   

• Initialization:
  union union_name variable_name = {value};
  

• Accessing Members:
  variable_name.member1 = new_value;
  

• Advantages:
  • Saves memory by allowing multiple members to share the same storage.
  • Useful for representing data that can take on different forms or interpretations.

Key Differences from Structures

Best Practices

• Use unions for representing data that can take on different forms or interpretations.
• Be careful when using unions to avoid unintended consequences due to shared memory.
• Use appropriate data types for members of unions to ensure correct memory allocation and operations.
• Consider using nested unions to create more complex data structures.

Example:

union data {
    int integer;
    float floating_point;
    char character;
};

int main() {
    union data value;

    value.integer = 10;
    printf("Integer value: %dn", value.integer);

    value.floating_point = 3.14;
    printf("Floating-point value: %fn", value.floating_point);

    value.character = 'A';
    printf("Character value: %cn", value.character);

    return 0;
}

In this example, the data union can store an integer, a floating-point number, or a character. Only one member can be active at a time. When you access one member, the value of the other members is undefined.