Difference between Structure and Union.
What is Structure?
Structure is a user-defined data type in C programming language that combines logically related data items of different data types together.
All the structure elements are stored at contiguous memory locations. Structure type variable can store more than one data item of varying data types under one name.
What is Union?
Union is a user-defined data type, just like a structure. Union combines objects of different types and sizes together. The union variable allocates the memory space equal to the space to hold the largest variable of union. It allows varying types of objects to share the same location.
Syntax of Declaring Structure
struct [name of the structure] {
type member1;
type member2;
type member3;
};
Structure is declared using the “struct” keyword and name of structure. Number 1, number 2, number 3 are individual members of structure. The body part is terminated with a semicolon (;).
Syntax of Declaring Union
union [name of union] {
type member1;
type member2;
type member3;
};
Union is declared using the “union” keyword and name of union. Number 1, number 2, number 3 are individual members of union. The body part is terminated with a semicolon (;).
Here is the important difference between structure and union:
Structure.
* You can use a struct keyword to define a structure.
* Every member within structure is assigned a unique memory location.
* Changing the value of one data member will not affect other data members in structure.
* It enables you to initialize several members at once
* The total size of the structure is the sum of the size of every data member.
* It is mainly used for storing various data types.
* It supports flexible array.
Union
* You can use a union keyword to define a union.
* In union, a memory location is shared by all the data members.
* Changing the value of one data member will change the value of other data members in union.
* It enables you to initialize only the first member of union.
* The total size of the union is the size of the largest data member.
* It is mainly used for storing one of the many data types that are available.
* It occupies space for a member having the highest size written in inner parameters.
* It does not support a flexible array.
Advantages of structure
Here are pros/benefits for using structure:
* Structures gather more than one piece of data about the same subject together in the same place.
* It is helpful when you want to gather the data of similar data types and parameters like first name, last name, etc.
* It is very easy to maintain as we can represent the whole record by using a single name.
* In structure, we can pass complete set of records to any function using a single parameter.
* You can use an array of structure to store more records with similar types.
Advantages of union
*It occupies less memory compared to structure.
*When you use union, only the last variable can be directly accessed.
*Union is used when you have to use the same memory location for two or more data members.
*It enables you to hold data of only one data member.
*Its allocated space is equal to maximum size of the data member.
Disadvantages of structure
*If the complexity of IT project goes beyond the limit, it becomes hard to manage.
*Change of one data structure in a code necessitates changes at many other places. Therefore, the changes become hard to track.
*Structure is slower because it requires storage space for all the data.
*You can retrieve any member at a time in structure whereas you can access one member at a time in the union.
*Structure occupies space for each and every member written in inner parameters while union occupies space for a member having the highest size written in inner parameters.
*Structure supports flexible array. Union does not support a flexible array.
Disadvantages of union
*You can use only one union member at a time.
*All the union variables cannot be initialized or used with varying values at a time.
*Union assigns one common storage space for all its members.
KEY DIFFERENCES:
*Every member within structure is assigned a unique memory location while in union a memory location is shared by all the data members.
*Changing the value of one data member will not affect other data members in structure whereas changing the value of one data member will change the value of other data members in union.
*Structure is mainly used for storing various data types while union is mainly used for storing one of the many data types.
*In structure, you can retrieve any member at a time on the other hand in union, you can access one member at a time.
*Structure supports flexible array while union does not support a flexible array.
