C Array of Structures and Unions

The structures are data types that are especially useful for creating collection items. We can make a collection of them using an array. Similarly, we can create array of Unions.

Why use an array of structures?

Consider a case, where we need to store the data of 5 students. We can store it by using the structure as given below.

snippet

#include
struct student
{
	char name[20];
	int id;
	float marks;
};
void main()
{
	struct student s1,s2,s3;
	int dummy;
	printf("Enter the name, id, and marks of student 1 ");
	scanf("%s %d %f",s1.name,&s1.id,&s1.marks);
	scanf("%c",&dummy);
	printf("Enter the name, id, and marks of student 2 ");
	scanf("%s %d %f",s2.name,&s2.id,&s2.marks);
	scanf("%c",&dummy);
	printf("Enter the name, id, and marks of student 3 ");
	scanf("%s %d %f",s3.name,&s3.id,&s3.marks);
	scanf("%c",&dummy);
	printf("Printing the details....\n");
	printf("%s %d %f\n",s1.name,s1.id,s1.marks);
	printf("%s %d %f\n",s2.name,s2.id,s2.marks);
	printf("%s %d %f\n",s3.name,s3.id,s3.marks);
}

Output

Enter the name, id, and marks of student 1 James 90 90 Enter the name, id, and marks of student 2 Adoms 90 90 Enter the name, id, and marks of student 3 Nick 90 90 Printing the details.... James 90 90.000000 Adoms 90 90.000000 Nick 90 90.000000

In the above program, we have stored data of 3 students in the structure. The complexity of the program will be increased if there are more students. If we have 30 student, we will have to declare 30 different structure variables and store them one by one. To avoid declaring the different structure variables, we can make a collection containing all the structures that store the information of different entities.

Array of Structures in C

An array of structures in C can be defined as the collection of multiple structures variables where each variable contains information about different entities. It is also known as the collection of structures.

The following code snippet shows how to create an array of structures and access a particular structure element’s member.

snippet

struct student {
    int rno;
    char name[50];
}
std1[10];
struct student std2[5];
std1[0].rno = 10;
std2[4].name = “umar”;

Below is an example of an array of structures that stores information of 5 students and prints it.

snippet

#include<stdio.h>
#include <string.h>  
struct student {
    int rollno;
    char name[10];
};
int main() {
    int i;
    struct student st[5];
    printf("Enter Records of 5 students");
    for (i = 0; i < 5; i++) {
        printf("\nEnter Rollno:");
        scanf("%d", & amp; st[i].rollno);
        printf("\nEnter Name:");
        scanf("%s", & amp; st[i].name);
    }
    printf("\nStudent Information List:");
    for (i = 0; i < 5; i++) {
        printf("\nRollno:%d, Name:%s", st[i].rollno, st[i].name);
    }
    return 0;
}

Output

Enter Records of 5 students Enter Rollno:1 Enter Name:John Enter Rollno:2 Enter Name:Ratan Enter Rollno:3 Enter Name:Vimal Enter Rollno:4 Enter Name:James Enter Rollno:5 Enter Name:Sarfraz Student Information List: Rollno:1, Name:John Rollno:2, Name:Ratan Rollno:3, Name:Vimal Rollno:4, Name:James Rollno:5, Name:Sarfraz

Array of Unions in C

The following code snippet shows how to create an array of unions and access a particular union element’s member.

snippet

union student {
    int rno;
    char name[50];
}
std1[10];
union student std2[5];
std1[0].rno = 10;
std2[4].name = “umar”;