How to declare, initialize and access array of structure

Quick links

Declare array of structure
Initialize structure array
Access structure array
Example program

Write a C program declare, initialize and access array of structure. In this post, I will explain how to declare, initialize and access array of structure in C programming. We will learn different ways of initializing structure array and accessing its.

Required knowledge

Basic C programming, Loop, Array, Structures

Declare, initialize and access array of structures in C programming language

In previous post we discussed how to declare and use structures in C language. Hence, I would not go deep discussing about basics of structures declaration.

How to declare array of structure?

Structure array declaration follows the normal array declaration syntax. Since, array of structure is a normal structure object only. Which we can declare structure array in two ways.

Along with structure declaration
After structure declaration

Declare array of structure along with structure declaration

The following code declares a structure to store student details. Along with the structure declaration it declares an array of structure object to store 100 student details.

// Array of structure declaration along with structure 
struct student 
{
    char  name[100];
    int   roll;
    float marks;
} stu[100];

Declare array of structure after structure declaration

The following code declares a student structure as we did above. After structure declaration it declares an array of student structure, capable of storing 100 student marks.

// Structure declaration 
struct student 
{
    char  name[100];
    int   roll;
    float marks;
};

// Structure array declaration
struct student stu[100];

How to initialize structure array?

Structure array initialization follows same syntax as you initialize single structure object. The only difference is here you can initialize more than one structure object at a time.

Example:

struct student stu[100] = 
{
    { "Pankaj", 12, 89.5f },
    { "Sweety", 15, 98.0f },
    { "Raani",  17, 90.0f },
    { "Bakhtawar Hameed", 2, 92.0f },
    { "Moody",    9, 60.2f }
};

How to access array of structure?

To access any structure object, you need to combine array indexed and structure member accessing technique. You can use either dot . or arrow -> (for pointers) operator to access structure array.

Example:

stu[0].name = "Pankaj";
stu[0].roll  = 12;
stu[0].marks = 89.5f;

The above code assigns data to first array object. You can also use loop to iterate for all array object.

Program to declare, initialize and access array of structure

/**
 * How to declare, initialize and access array of structures in C
 */

#include <stdio.h>
#define MAX_STUDENTS 5


// Student structure type declaration
struct student 
{
    char    name[100];
    int     roll;
    float   marks;
};


int main()
{
    // Declare array of structure variables
    struct student stu[MAX_STUDENTS];
    int i;

    // Read all 5 student details from user
    printf("Enter %d student details\n", MAX_STUDENTS);
    for ( i = 0; i < MAX_STUDENTS; i++ )
    {
        printf("Student %d name: ", (i + 1));
        gets(stu[i].name);


        printf("Student %d roll no: ", (i + 1));
        scanf("%d", &stu[i].roll);

        printf("Student %d marks: ", (i + 1));
        scanf("%f", &stu[i].marks);
        getchar();  // <-- Eat extra new line character

        printf("\n");
    }

    

    // Print all student details
    printf("\n\nStudent details\n");
    printf("---------------------------\n");
    for ( i = 0; i < MAX_STUDENTS; i++ )
    {
        printf("Name : %s\n",   stu[i].name);
        printf("Roll : %d\n",   stu[i].roll);
        printf("Marks: %.2f\n", stu[i].marks);
        printf("---------------------------\n");
    }


    return 0;
}

Output

Enter 5 student details
Student 1 name: Pankaj
Student 1 roll no: 12
Student 1 marks: 89.5

Student 2 name: Sweety
Student 2 roll no: 15
Student 2 marks: 98.0

Student 3 name: Raani
Student 3 roll no: 17
Student 3 marks: 90.0

Student 4 name: Bakhtawar Hameed
Student 4 roll no: 2
Student 4 marks: 92.0

Student 5 name: Moody
Student 5 roll no: 9
Student 5 marks: 60.2



Student details
---------------------------
Name : Pankaj
Roll : 12
Marks: 89.50
---------------------------
Name : Sweety
Roll : 15
Marks: 98.00
---------------------------
Name : Raani
Roll : 17
Marks: 90.00
---------------------------
Name : Bakhtawar Hameed
Roll : 2
Marks: 92.00
---------------------------
Name : Moody
Roll : 9
Marks: 60.20
---------------------------

Happy coding