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This tutorial explains how to create a structure array in C language, which is a collection of multiple structure variables, each of which contains information about a different entity.

Structure arrays in C

An array is a sequential collection of elements of the same data type, and a structure is a user-defined data type. The declaration of an array of a structure is the same as an array of a primitive data type, but using the data type that the structure has its elements.

Consider an Studentexample of a structure called , shown below.

struct Student
{
    int rollNumber;
    char studentName[10];
    float percentage;
};

We can declare an array of structures as follows.

struct Student studentRecord[5];

Here, studentRecordit is an array of 5 elements, each of which is of type Studentstruct. Individual elements []are accessed using index notation and members (.)are accessed using the dot operator.

studentRecord[0]Points to the element of the array 0th, studentRecord[1]points to the element of the array 1th.

Similarly,

• studentRecord[0].rollNumberRefers to the member in the 0th element of the array rollNumber.
• studentRecord[0].studentNameRefers to the member in the 0th element of the array studentName.
• studentRecord[0].percentageRefers to the member of the 0th element of the array percentage.

structThe complete program to declare an array in C language is as follows.

#include<stdio.h>
#include<string.h>

struct Student
{
    int rollNumber;
    char studentName[10];
    float percentage;
};

int main(void)
{
    int counter;
    struct Student studentRecord[5];

    printf("Enter Records of 5 students");

    for(counter=0; counter<5; counter++)
    {
        printf("\nEnter Roll Number:");
        scanf("%d",&studentRecord[counter].rollNumber);
        printf("\nEnter Name:");
        scanf("%s",&studentRecord[counter].studentName);
        printf("\nEnter percentage:");
        scanf("%f",&studentRecord[counter].percentage);

    }

    printf("\nStudent Information List:");

    for(counter=0; counter<5; counter++)
    {
        printf("\nRoll Number:%d\t Name:%s\t Percentage :%f\n",
               studentRecord[counter].rollNumber,studentRecord[counter].studentName, studentRecord[counter].percentage);
    }
    return 0;
}

Output:

Enter Record of 5 students
Enter Roll number:1
Enter Name: John
Enter percentage: 78

Enter Roll number:2
Enter Name: Nick
Enter percentage: 84

Enter Roll number:3
Enter Name: Jenny
Enter percentage: 56
  
Enter Roll number:4
Enter Name: Jack
Enter percentage: 77
   
Enter Roll number:5
Enter Name: Peter
Enter percentage: 76
    
   Student Information List
   Roll Number: 1		Name: John		percentage:78.000000
   Roll Number: 2		Name: Nick		percentage:84.000000
   Roll Number: 3		Name: Jenny		percentage:56.000000
   Roll Number: 4		Name: Jack		percentage:77.000000
   Roll Number: 5		Name: Peter		percentage:76.000000
       

malloc()Create an structarray using the C function

In C language, there is another way to make structarrays, you can use malloc()the function to allocate memory for structthe array. This is called dynamic memory allocation.

malloc()(Memory Allocation) function is used to dynamically allocate a large block of memory of a specified size. This function returns a voidpointer of type .

The returned pointer can be cast to any form of pointer. It initializes each block with default garbage values.

malloc()The syntax of the function is as follows.

ptrVariable = (cast-type*) malloc(byte-size)

The complete program to dynamically create an array of structures is as follows.

#include<stdio.h>
int main(int argc, char** argv)
{
    typedef struct
    {
        char* firstName;
        char* lastName;
        int rollNumber;

    } STUDENT;

    int numStudents=2;
    int x;
    STUDENT* students = malloc(numStudents * sizeof *students);
   
    for (x = 0; x < numStudents; x++)
    {
        students[x].firstName=(char*)malloc(sizeof(char*));
       
        printf("Enter first name :");
        scanf("%s",students[x].firstName);
        students[x].lastName=(char*)malloc(sizeof(char*));
        printf("Enter last name :");
        scanf("%s",students[x].lastName);
        printf("Enter roll number  :");
        scanf("%d",&students[x].rollNumber);

    }

    for (x = 0; x < numStudents; x++)
        printf("First Name: %s, Last Name: %s, Roll number: %d\n",students[x].firstName,students[x].lastName,students[x].rollNumber);

    return (0);
}

Output:

Enter first name:John
Enter last name: Williams
Enter roll number:1

Enter first name:Jenny
Enter last name: Thomas
Enter roll number:2
    
First Name: John	Last Name: Williams		Roll Number:1
First Name: Jenny	Last Name: Thomas		Roll Number:2