Structure in C is a user-defined data type available in C that allows to combining of data items of different kinds. Structures are used to represent a record.
Defining a structure : To define a structure, you must use the struct statement. The struct statement defines a new data type, with more than or equal to one member.
The format of the srtuct statement is as follows :
struct [structure name] {
member definition;
member definition; I
...
member definition;
};
(OR)
struct [structure name]
{
member definition;
member definition;
...
member definition;
}structure variable declaration;
Union in C is a special data type available in C that allows storing different data types in the same memory location. You can define a union with many members, but only one member can contain a value at any given time. Unions provide an efficient way of using the same memory location for multiple purposes.
Defining a Union : To define a union, you must use the union statement in the same way as you did while defining a structure. The union statement defines a new data type with more than one member for your program.
The format of the union statement is as follows :
union [union name]
{
member definition;
member definition;
...
member definition;
};
(OR)
union [union name]
{
member definition;
member definition;
...
member definition;
}union variable declaration;
Similarities between Structures and Unions :
- Both are user-defined data types used to store data of different types as a single unit.
- Their members can be objects of any type, including other structures and unions or arrays. A member can also consist of a bit field.
- Both structures and unions support only assignment = and sizeof operators. The two structures or unions in the assignment must have the same members and member types.
- A structure or a union can be passed by value to functions and returned by value by functions. The argument must have the same type as the function parameter. A structure or union is passed by value just like a scalar variable as a corresponding parameter.
- ‘.’ operator or selection operator, which has one of the highest precedences, is used for accessing member variables inside both the user-defined datatypes.
