The C programming language has several built-in data kinds. It also enables users to design their data types. Five approaches for constructing custom data include bit-field, structure, union, typedef, and enumeration. In this blog, we will grasp what structure and union are. Both structure and union are user-defined data types in C programming that may hold any data type. While both structure and union appear to accomplish similar purposes, there are many distinctions between them. Let’s grasp the difference between structure and union.
Definition of Structure in C
A structure is a specialized data type in the C language. Facilities may store numerous members of various data kinds under a single unit. The components of a system are stored in contiguous memory regions and may be retrieved and accessed at any time.
The structure is a user-defined data type in C language which allows us to combine data of different types together. Structure helps to construct a complex data type that is more meaningful. It is somewhat similar to an Array, but an array holds data of similar type only. But the structure, on the other hand, can store data of any type, which is practical more useful.
For example: If I have to write a program to store Student information, which will have Student's name, age, branch, permanent address, father's name, etc, which included string values, integer values, etc, how can I use arrays for this problem, I will require something which can hold data of different types together.
In structure, data is stored in form of records.
struct keyword is used to define a structure. struct defines a new data type which is a collection of primary and derived data types.
Syntax of Declaring a Structure
struct [structure name]
{
type member_1;
type member_2;
. . .
type member_n;
};
Example Of Structure
struct student
{
int rollno;
char name[50];
string phone;
};
Definition of Union in C
A Union is a user-defined data type. It is exactly like the structure, except that all of its members start at the same point in memory. The union unites numerous objects of different data kinds in the same memory area. A user may define a union with multiple members, but only one member can hold a value at any one moment. The storage space allotted for the union variable is equal to the entire area needed for the most prominent data member of the union.
Union offers such variables that may be accessed in different methods at the same memory place at the same time. A union provides an effective technique of utilizing a single memory region for numerous operations.
What is Union Statement?
The union statement is used for defining a union. It creates a new data type that can hold several member variables of various data types in the same memory region. The syntax to define union using the union keyword is equivalent to constructing a structure.
Unions are conceptually similar to structures. The syntax to declare/define a union is also similar to that of a structure. The only differences is in terms of storage. In structure each member has its own storage location, whereas all members of union uses a single shared memory location which is equal to the size of its largest data member.
Syntax of Declaring a Union
union [union name]
{
type member_1;
type member_2;
. . .
type member_n;
};
Example Of Union
union Student {
char name[32];
int age;
string email;
};
Similarities between Structure and Union in C
- Both structure and union are special data types for storing multiple types of data as a single object.
- Structure and union members can be any sort of object, including other structures, unions, and arrays.
- Structures and unions can be provided by value to a function, and functions can also return to the value. The type of the argument must match that of the function parameter.
- The '.' operator is used to access members.
Difference between Structure and Union in C
A structure and a union incorporate diverse information linked to a particular object. The critical distinction between the two is how particular information is stored and accessible. The table below outlines the fundamental differences between structure and union:
|
Structure
|
Union
|
- We use the struct command to define a structure.
|
- We utilize the union keyword to define a union.
|
- Every member is allocated a unique memory location.
|
- All the data members share a memory location.
|
- Change in the value of one data member does not impact other data members in the structure.
|
- Change in the value of one data member impacts the value of other data members.
|
- You may initialize many members at a time.
|
- You may initialize just the first member at once.
|
- A structure may hold various values of the distinct parts.
|
- A union keeps one value at a time for all of its members
|
- A structure’s total size is the sum of the size of every data component.
|
- A union’s total size is the size of the biggest data member.
|
- Users may access or recover any member at a time.
|
- You may access or recover just one member at a time.
|
Advantages of Using Structure
- Structures bring together multiple pieces of information about the same issue in one place.
- It comes in handy when you need to collect data of comparable data kinds and attributes, such as first name, last name, and so on.
- It's simple to maintain because we can represent the entire record with a single name.
- We can pass a complete collection of records to any function using a single argument in structure.
- An array of structure can be used to store additional records of the same type.
Advantages of Using Union
- When compared to structure, it takes up less memory.
- Only the last variable can be directly accessed while using union.
- When you need to use the same memory address for two or more data members, you use union.
- It allows you to store only one data member's data.
- Its assigned space is equal to the data member's maximum size.
Disadvantages of Using Structure
- When an IT project's complexity exceeds a certain threshold, it becomes difficult to manage.
- In a code, changing one data structure involves modifications in many other locations. As a result, it's difficult to keep track of the changes.
- Because all of the data must be stored, structure takes longer.
- In structure, you can retrieve any member at any moment, however in the union, you can only access one member at a time.
- Each member written in inner parameters takes up space in the structure, whereas the largest member written in inner parameters takes up space in the union.
- Flexible array is supported by the structure. A flexible array is not supported by Union.
Disadvantages of Using Union
- Only one union member can be used at a time.
- At the same time, none of the union variables can be initialised or utilised with changeable values.
- For all of its members, the union assigns a single shared storage space.
Conclusion
In this blog, we explored how structure and union operate and how they vary from one another. Both structure and union are user-defined data types in C programming that contain numerous members of distinct data types. Structures are employed when we need to store different values for all the members in a unique memory location, whereas unions assist manage memory effectively.
