Pointer to array of structures

Posted on June 20, 2020

C program to show the usage of pointer to array of structures.

Program 

#include<stdio.h>
#include<conio.h>

struct person
{
    char name[20];
    int age;
    float weight;
};

void main()
{
   struct person p1[10];
    struct person *ptr;
    int i, n;

    printf("Enter the number of persons\t:");
    scanf("%d",&n);

    ptr = &p1;

    for(i=0;i<n;i++)
    {
        printf("\nEnter the details of person %d",i+1);
        printf("\nEnter name\t:");
        scanf("%s",(ptr+i)->name);
        printf("Enter age\t:");
        scanf("%d",&(ptr+i)->age);
        printf("Enter weight\t:");
        scanf("%f",&(ptr+i)->weight);
    }

    for(i=0;i<n;i++)
    {
        printf("\n\nData of the person %d is",i+1);
        printf("\nName\t:%s",(ptr+i)->name);
        printf("\nAge\t:%d",(ptr+i)->age);
        printf("\nWeight\t:%f",(ptr+i)->weight);
    }

    getch();
}

Output 

Enter the number of persons     :2

Enter the details of person 1
Enter name      :neha
Enter age       :30
Enter weight    :75.3

Enter the details of person 2
Enter name      :nikhil
Enter age       :32
Enter weight    :95.4


Data of the person 1 is
Name    :neha
Age     :30
Weight  :75.300000

Data of the person 2 is
Name    :nikhil
Age     :32
Weight  :95.400000

Explanation

In the above program, a structure 'person' is defined and an arraty 'p1[10]' of struct person type is declared. A struct pointer 'ptr' is also declared. The starting address of 'p1[0]' is stored in the 'ptr' pointer using
ptr = &p1;

Now, you can access the members of 'p1[]' using the 'ptr' pointer. To access members of structure using the structure variable, we used the dot (.) operator. But when we have a pointer of structure type, we use arrow (->) to access structure members.
ptr->age //p1[0]->age
ptr->weight //p1[0]->weight
To access the members of p1[1], we will use (ptr+1) i.e.
(ptr+1)->age
(ptr+1)->weight
In general, to access the members of p1[i], we will use (ptr+i) i.e.
(ptr+i)->age
(ptr+i)->weight

Note that,
(ptr+i)->age is equivalent to (*(ptr+i)).age
(ptr+i)->weight is equivalent to (*(ptr+i)).weight
Program for the same is shown in "Method 2" tab.

Program 

#include<stdio.h>
#include<conio.h>

struct person
{
    char name[20];
    int age;
    float weight;
};

void main()
{
    struct person p1[10];
    struct person *ptr;
    int i, n;

    printf("Enter the number of persons\t:");
    scanf("%d",&n);

    ptr = p1;

    for(i=0;i<n;i++)
    {
        printf("\nEnter the details of person %d",i+1);
        printf("\nEnter name\t:");
        scanf("%s",(*(ptr+i)).name);
        printf("Enter age\t:");
        scanf("%d",&(*(ptr+i)).age);
        printf("Enter weight\t:");
        scanf("%f",&(*(ptr+i)).weight);
    }

    for(i=0;i<n;i++)
    {
        printf("\n\nData of the person %d is",i+1);
        printf("\nName\t:%s",(*(ptr+i)).name);
        printf("\nAge\t:%d",(*(ptr+i)).age);
        printf("\nWeight\t:%f",(*(ptr+i)).weight);
    }

    getch();
}

Output 

Enter the number of persons     :2

Enter the details of person 1
Enter name      :neha
Enter age       :30
Enter weight    :75.3

Enter the details of person 2
Enter name      :nikhil
Enter age       :32
Enter weight    :95.4


Data of the person 1 is
Name    :neha
Age     :30
Weight  :75.300003

Data of the person 2 is
Name    :nikhil
Age     :32
Weight  :95.400002