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Explain the pointers to unions in C language
A union is a memory location that is shared by several variables of different data types.
Syntax
The syntax for the pointers to unions in C programming is as follows −
union uniontag{
datatype member 1;
datatype member 2;
----
----
datatype member n;
};Example
The following example shows the usage of union of structure.
union sample{
int a;
float b;
char c;
};Declaration of union variable
Following is the declaration for union variable. It is of three types as follows −
Type 1
union sample{
int a;
float b;
char c;
}s;Type 2
union{
int a;
float b;
char c;
}s;Type 3
union sample{
int a;
float b;
char c;
};
union sample s;When union is declared, the compiler automatically creates largest size variable type to hold variables in the union.
At any time only one variable can be referred.
Same syntax of structure is used to access a union member.
The dot operator is for accessing members.
The arrow operator ( ->) is used for accessing the members using pointer.
We have pointers to unions and can access members using the arrow operator (->) just like structures.
Example
The following program shows the usage of pointers to union in C programming −
#include <stdio.h>
union pointer {
int num;
char a;
};
int main(){
union pointer p1;
p1.num = 75;
// p2 is a pointer to union p1
union pointer* p2 = &p1;
// Accessing union members using pointer
printf("%d %c", p2->num, p2->a);
return 0;
}Output
When the above program is executed, it produces the following result −
75 K
Example 2
Consider the same example with different input.
#include <stdio.h>
union pointer {
int num;
char a;
};
int main(){
union pointer p1;
p1.num = 90;
// p2 is a pointer to union p1
union pointer* p2 = &p1;
// Accessing union members using pointer
printf("%d %c", p2->num, p2->a);
return 0;
}Output
When the above program is executed, it produces the following result −
90 Z
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