Structures and Unions
In C, structures and unions are composite data types that allow you to group together variables of different data types.
A structure is a user-defined data type that groups together variables of different data types under a single name. The general syntax for declaring a structure in C is:
struct structure_name {
data_type1 variable1;
data_type2 variable2;
...
};
For example, the following code declares a structure named student that holds information about a student:
struct student {
int roll_no;
char name[100];
float marks;
};
You can create variables of a structure type using the structure name and access its members using the dot operator (.).
For example, the following code creates a variable of type student named s and accesses its members:
#include <stdio.h>
struct student {
int roll_no;
char name[100];
float marks;
};
int main() {
struct student s;
s.roll_no = 123;
strcpy(s.name, "John Doe");
s.marks = 85.5;
printf("Roll No: %d\n", s.roll_no);
printf("Name: %s\n", s.name);
printf("Marks: %.2f\n", s.marks);
return 0;
}
The output of the above program will be:
Roll No: 123
Name: John Doe
Marks: 85.50
A union is similar to a structure, but it allows you to store multiple values of different data types in the same memory location. The general syntax for declaring a union in C is:
union union_name {
data_type1 variable1;
data_type2 variable2;
...
};
For example, the following code declares a union named value that holds either an integer or a float:
union value {
int i;
float f;
};
You can create variables of a union type using the union name and access its members using the dot operator (.).
For example, the following code creates a variable of type value named v and accesses its members:
#include <stdio.h>
union value {
int i;
float f;
};
int main() {
union value v;
v.i = 123;
printf("Integer value: %d\n", v.i);
v.f = 123.456;
printf("Float value: %.2f\n", v.f);
return 0;
}
The output of the above program will be:
Integer value: 123
Float value: 123.46
Note that when you access one member of a union, the values of the other members are lost. Unions are useful when you want to save memory by using the same memory location for different values of different data types.
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